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how much does pine shrink in a kiln?

Started by Compensation, February 28, 2013, 10:15:33 PM

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Compensation

This weekend i wanna cut up 3 pine trees into 2x2's (1.5x1.5) to use as framing for my bar walls. The stuff you get at lowes is like 1.5x1.5" right? Well i dont want to plane it down after i pull it out of the kiln. What should i cut them down to on the mill to get close to 1.5x1.5" after any shrinkage?
Thanks!
D4D caterpillar, lt10 Woodmizer, 8x12 solar kiln, enough Stihl's to make my garages smell like their factory :) Ohh and built Ford tough baby!

beenthere

Which pine?

There several tables available on the net, and here is one example.
http://pods.dasnr.okstate.edu/docushare/dsweb/Get/Document-2535/NREM-5009web.pdf

Also
http://www.fs.fed.us/ccrc/topics/urban-forests/docs/physical%20properties%20and%20moisture%20relations%20of%20wood.pdf

Shows the shrinkage for radial and tangential directions.

And WDH has your best bet covered. :)
south central Wisconsin
It may be that my sole purpose in life is simply to serve as a warning to others

WDH

It is going to be hard to get them exact without planing.  Wood shrinks differently depending on the orientation of the growth rings, so each piece may behave just a bit different.  Planing may be your best option.
Woodmizer LT40HDD35, John Deere 2155, Kubota M5-111, Kubota L2501, Nyle L53 Dehumidification Kiln, and a passion for all things with leafs, twigs, and bark.  hamsleyhardwood.com

Compensation

I am not good on my trees yet. One is a blue spruce, one had 5"pine cones, and the other i dont think had cones but it was lighter color and killed my grass like crazy :)

I have a nice craftsman pro planer so if its inevitable then i can but just wanted to avoid it if i could.
D4D caterpillar, lt10 Woodmizer, 8x12 solar kiln, enough Stihl's to make my garages smell like their factory :) Ohh and built Ford tough baby!

Ianab

You want a ""rule of thumb"?

Cut them 1.75"

Then you should have enough left to plane them to the exact size, without spending all day making shavings.

Ian
Weekend warrior, Peterson JP test pilot, Dolmar 7900 and Stihl MS310 saws and  the usual collection of power tools :)

GeneWengert-WoodDoc

Make sure that you saw them so that the annual rings run parallel to two faces and perpendicular to the other two faces.  In other words, avoid having the rings go diagonally, from one corner to the opposite corner.  With diagonal rings, the pieces will become diamond shaped as they dry.

As a rule of thumb, if you dry to 10% MC, most conifers will shrink 5% in one direction (running parallel,to the rings when looking at the end grain) and 2-1/2% in the other.  So, you could technically cut the piece 1.58" x 1.54", with the large dimension running parallel to the rings, which would also be the width of flatsawn lumber.

But wood likes to warp a little bit and your saw will have a little roughness.  Also, the shrinkage values are average values and so we would see half the pieces with a little less and half with more shrinkage.  So, we need to add a JIC (just in case) number...perhaps 0.09" but this is just an estimate.  Plus, a planer does not like to remove under 1/32" or 0.03".  So, add 0.12" to both dimension numbers.  Then add a little more to account for the fact that when you set 1.70" x 1.66" on the mill there will be a little variation from piece to piece and also within an individual piece, so add 0.05".

Bottom line is that Ianab knows what he is talking about!
Gene - Author of articles in Sawmill & Woodlot and books: Drying Hardwood Lumber; VA Tech Solar Kiln; Sawing Edging & Trimming Hardwood Lumber. And more

Compensation

This is why i signed up to FF. I could spend hours online going no where, and you guys give the right answer within a few hours. Amazing! Thanks so much!
D4D caterpillar, lt10 Woodmizer, 8x12 solar kiln, enough Stihl's to make my garages smell like their factory :) Ohh and built Ford tough baby!

SwampDonkey

We've (forum) looked at the tables of empirical data a few times to 'estimate' shrinkage and I think we came to the conclusion to leave 1/8" per 2" of material. If your not planing. Add a little more for planing as Ian suggested

For academic purposes, when your using math, I've used figures from 'Textbook of Wood Technology' or the "Wood Handbook", same numbers. 99.99% aren't interested in that, unless out of curiosity.

Anyway, to be practical assume an additional 1/8" for shrinkage per 2" of thickness/width plus another 1/8" for planing and uniformity as suggested.
"No amount of belief makes something a fact." James Randi

1 Thessalonians 5:21

2020 Polaris Ranger 570 to forward firewood, Husqvarna 555 XT Pro, Stihl FS560 clearing saw and continuously thinning my ground, on the side. Grow them trees. (((o)))

GeneWengert-WoodDoc

just remember that the table values are the average, not max or min.  The 1/8" rule is for flatsawn.
Gene - Author of articles in Sawmill & Woodlot and books: Drying Hardwood Lumber; VA Tech Solar Kiln; Sawing Edging & Trimming Hardwood Lumber. And more

Planman1954

Make sure that you weight them down to prevent warpage. They will usually bend when drying!
Norwood Lumbermate 2000 / Solar Dry Kiln /1943 Ford 9n tractor

SwampDonkey

Gene, yes flat sawn. And yes the empirical numbers are based on stats from sampling.  But I think most will carry it forward for quartered to, that way only gotta remember one number. Even though quartered has less shrinkage. Again it's a uniformity factor if we're planing. kinda like splitting hairs. ;D A 1/16" per 2" might get you by on the radial shrinkage. I'd rather stick with the 1/8". The thing is, you can't be certain a piece is quarter all the way down, say for 10', the grain could run out and then look flat saw on the far end. Easier to go with the 1/8" rule.
"No amount of belief makes something a fact." James Randi

1 Thessalonians 5:21

2020 Polaris Ranger 570 to forward firewood, Husqvarna 555 XT Pro, Stihl FS560 clearing saw and continuously thinning my ground, on the side. Grow them trees. (((o)))

GeneWengert-WoodDoc

Maybe I was not clear enough...let me try again.  The table values for U.S. softwoods, tangential direction, run from 6.0 to 7.8% from green to oven dry.  As we usually dry only to 10% MC at the driest, then we would use 2/3 of the table values for green to 0% MC.   Then because a piece of wood is seldom true flatsawn, but has some angle, then the shrinkage will be even less than the table vales.  The table values are for thin pieces of wood (1/16")...Thick pieces shrink less.  However, the table values are averages, so half the pieces will shrink slightly more than the table.  So, with these plusses and minuses, the table value adjusted for MC is a good estimate...at 10% MC, most softwoods will shrink a maximum of 4.0% 5.5%, depending an species.  Now the 1/8" rule for a piece of nominal 2" width (actual when sawing is 1.75") is 7.1% Over size.  So, the 1/8" for every 2" rule for shrinkage alone (and not sawing variation, planer allowance, warp) is quite a bit more than needed for shrinkage only.  But it is not enough for the other variations, so that is why 1/4" thicker was suggested by Ianab and confirmed by the calculations I made.  The point is that shrinkage alone does not give us a good estimate of the green size required
Gene - Author of articles in Sawmill & Woodlot and books: Drying Hardwood Lumber; VA Tech Solar Kiln; Sawing Edging & Trimming Hardwood Lumber. And more

SwampDonkey

Yes, even a 1/8th" per 2" can be a little on the high side depending on how low you go in MC for the the application of the wood.

For instance Loblolly pine

Sp gravity green is 0.47, Vsh%= 12.3% (green to OD), tangential shrinkage is 7.4%, target MC = 10%, want say a 1.5" x 7.5" flat sawn.

Fibre saturation point is 12.3%/0.47 = 26.17%

→10% = 7.4 * (26.17-10)= 4.57%
Tsh        26.17

width = 7.5"
            (1-0.0457)
         = 7.859  not quite 3/8 difference but more than 5/16th for shrinkage allowance.

Really just academic arguments. It doesn't appear to me that the estimate is showing too much waste in thickness allowance for shrinkage.

I think we all agree there are other factors at play, whether stated or not. But it's always good to mention them on this topic. :)

"No amount of belief makes something a fact." James Randi

1 Thessalonians 5:21

2020 Polaris Ranger 570 to forward firewood, Husqvarna 555 XT Pro, Stihl FS560 clearing saw and continuously thinning my ground, on the side. Grow them trees. (((o)))

GeneWengert-WoodDoc

The fsp for almost all US woods is 30% MC.  I have never seen dividing the Volumetric shrinkage by SG to get the fsp.  For redwood, it gives a fsp of 18.9%, no. Red oak 21%, so red oak 26%.  These values are all incorrect.  I suggest that you redomyour calculation using 30% MC for fsp.  We sometimes see tropical woods with a fsp depressed to 22 to 25% MC but that is rare.  For reference, see Chapter 3 of the WOOD HANDBOOK, for instance figure 3-6 and associated text.
Gene - Author of articles in Sawmill & Woodlot and books: Drying Hardwood Lumber; VA Tech Solar Kiln; Sawing Edging & Trimming Hardwood Lumber. And more

SwampDonkey

30 % for FSP is used by the Wood Handbook for simplification as a good guideline. This has been discussed on the forum before.

However, 'The Wood Handbook' uses the same formula for shrinkage and the same values that I use. Only difference is I calculate FSP instead of using the 'standardized' 30 %, which in itself is subject to large standard deviations.

The calculation of FSP must be new to you, because it's straight from Dr. Sebastian's "Fundamental Physical Properties of Wood" at the Dept of Forest Resources at UNB. He was the wood science professor for a number of years, now deceased.  The formula is also used by many authors and unless you have an account online to access research and texts Google won't do much good.

If you use the magic 30 % you'll have your 1/8" shrinkage per 2" in fact a little more. So to say the 1/8" per 2" rule is too much, is false.
"No amount of belief makes something a fact." James Randi

1 Thessalonians 5:21

2020 Polaris Ranger 570 to forward firewood, Husqvarna 555 XT Pro, Stihl FS560 clearing saw and continuously thinning my ground, on the side. Grow them trees. (((o)))

GeneWengert-WoodDoc

If you have a page number, that would help. 

It is not mentioned in the WOOD HANDBOOK.  I do not see it in TEXTBOOK OF WOOD TECHNOLOGY.  Although there is indeed some variation in the value of fsp, I cannot believe the values for redwood or red oak that I quoted, 19% and 21%.  I just checked basswood and that has volumetric of 15.8 and the SG is .38, so that gives the fsp of 42%, which I cannot imagine at all.  I would think that if fsp actually varied that much, it would have been mentioned.  I have carved basswood that was stored at 65% RH and it was at 12% MC which is,normal for 30% fsp.

I did do some research on the value of MC for wood stored at 80% (16% EMC) RH for my work at the Univ of Wisc in 1976 and I did not see more than two percent variation maximum for different species.
Gene - Author of articles in Sawmill & Woodlot and books: Drying Hardwood Lumber; VA Tech Solar Kiln; Sawing Edging & Trimming Hardwood Lumber. And more

SwampDonkey

First off, we have to make a distinction here between variation within a tree or species, and that magic number of 30. A tree may vary by 2-3% as you already suggest. But, if you look in the Textbook of Wood Technology', 4 ed, pg 281 a couple examples are given showing this variation, but one species is as low as 27% and another as high as 36%. And also note that FSP is influenced by specific gravity (green) as mentioned in the text. So, now I guess you can except that I just mentioned (with text reference) two species are 9 points apart, one as much as 6 points above the magic 30%. ;D

Consider that most of the sapwood is in the slab pile when sawed. Take the 'heartwood' of the hard pines like red pine and loblolly, the green condition is around 32 MC%. You trying to convince me that green condition of hard pine heartwood equals FSP? That would suggest not a lot of water in cell lumens, in fact just about dried up. In drought times that could cause some unfavorable internal stresses.   And yes bound water loss causes shrinkage, not free water. The example in the document below shows that red pine FSP is below 28%. Basswood has a MC 81% in the heart when green, where as beech has 55% and much denser. When you use the values for beech FSP = 17.2/.56 = 31 %, white oak 15.9/0.59 = 27%

Attached is a PDF with excerpts on FSP from Dr. Sebastian's 'Fundamental Physical Properties of Wood'. How it is derived and an example on the following page. Any page references in the document refer to the 'Textbook of Wood Technology', 4th ed.

There are a number of formula's in the 'Wood Handbook' and 'Textbook of Technology' However, there are a few more you will not find there.

Believe me I don't dream this stuff up. ;D
"No amount of belief makes something a fact." James Randi

1 Thessalonians 5:21

2020 Polaris Ranger 570 to forward firewood, Husqvarna 555 XT Pro, Stihl FS560 clearing saw and continuously thinning my ground, on the side. Grow them trees. (((o)))

GeneWengert-WoodDoc

Thanks for posting.  I do believe that the error that Dr. Sebastian makes is when he replaces V (bound water) with Vg - Vo.  That is, the shrinkage of wood when going from green to oven dry does not represent the volume of water lost.  This is an incorrect assumption.  On a molecular level, when a water molecule leaves the wood, the wood does not close up the gap or void left.  The reason is due to the crystallinity of the cellulose.  Dr. Chris Skaar discusses this in his book WATER IN WOOD.

As another example, consider Brazilian rosewood with a volumetric shrinkage of 8.5 and SG of 0.8 which gives a fsp of 11% MC, which is not even close.

Or consider balsa wood with volumetric shrinkage of 10.8 and SG of 0.16, giving a fsp of over 60% MC.

If indeed the fsp varied that much, I cannot image why the Wood Handbook would not even mention it.  Likewise, the Textbook of Wood Technology.
Gene - Author of articles in Sawmill & Woodlot and books: Drying Hardwood Lumber; VA Tech Solar Kiln; Sawing Edging & Trimming Hardwood Lumber. And more

GeneWengert-WoodDoc

Regarding the amount of liquid water in species that have a green MC close to 30% MC, we find that in those species we do not have to dry the heartwood in order to treat the wood with preservatives.  There is indeed very little water present.  Because the heartwood does not participate in movement of water within the tree, the lack of water in the heartwood is not a issue in times of drought.
Gene - Author of articles in Sawmill & Woodlot and books: Drying Hardwood Lumber; VA Tech Solar Kiln; Sawing Edging & Trimming Hardwood Lumber. And more

SwampDonkey

Not as far as moving water up the stem, but drying stress dropping below FSP.

If volumetric shrinkage isn't caused by water lost (water has volume) than you have me baffled. ;D Cell lumens is another matter, that is free water in there. No shrinkage, it's in the cells walls from loss of bound water that shrinkage occurs. No two atoms or molecules can occupy the same space at once.

You misinterpret the formula, he is talking volume of bound water.
"No amount of belief makes something a fact." James Randi

1 Thessalonians 5:21

2020 Polaris Ranger 570 to forward firewood, Husqvarna 555 XT Pro, Stihl FS560 clearing saw and continuously thinning my ground, on the side. Grow them trees. (((o)))

SwampDonkey

And heartwood has a dead zone and a live zone. The live zone functions the same as the sapwood but in some trees it has color changes from extractives, both are xylem and conducting tissue. The sapwood is just newer xylem. If you have ever harvested trees, you will notice water comes up not only in the outter portion of the stump, but also toward the pith until in the dead zone. With some species water will flow in reverse when severed from the stump. A number of forum members will bear witness to this. Misinterpreting this can lead one to believe there might be confusion over xylem and phloem tissue. Phloem is what brings stuff down from the food factory dissolved in water to feed the tree and rays deliver it and oxygen radially to live cells to both store food and live off it. Pores are also involved. Rays extend from the bark of the tree inward.

Heartwood classification is presented on pages 24-25 in "Text of Wood Technology", 4th ed.
"No amount of belief makes something a fact." James Randi

1 Thessalonians 5:21

2020 Polaris Ranger 570 to forward firewood, Husqvarna 555 XT Pro, Stihl FS560 clearing saw and continuously thinning my ground, on the side. Grow them trees. (((o)))

GeneWengert-WoodDoc

I am indeed talking about bound water and its relationship to shrinkage...that is, shrinkage is indeed caused by bound water loss.  The amount of bound water  volume loss is, however, not equal to the shrinkage volume.  The fsp calculations I gave show that is not true....fsp is not 60% MC.  The reason is that when a water molecule leaves the wood, the void created is not closed completely by the movement of the wood molecules.  One effect, if it were true, is that the curve of shrinkage versus MC would be a perfectly straight line, but all the data shows that is not true.  One reason for the shape of the curve at high MCs is that the water molecules at high MC are not held by the wood molecules directly but are in several layers and are bound to each other via hydrogen bonds rather than to cellulose OH bonds.  So, when high MC bound water leaves, the water molecules move to satisfy the bond and not necessarily the wood.  Siau wrote a good explanation in his book, as well as Skaar's book.

Regarding dead or alive, you are stating that chapter 3 page 3 of the WOOD HANDBOOK (FPL 190, 2010 version) is incorrect?  Here is the definition in the glossary.  "Heartwood. The wood extending from the pith to the sapwood, the cells of which no longer participate in the life processes of the tree. Heartwood may contain phenolic compounds, gums, resins, and other materials that usually make it darker and more decay resistant than sapwood"

In the TEXTBOOK OF WT, the definition of heartwood is the loss on the nuclei from the cell, which means it is dead.  P.56.  I do not debate that sapwood in transition to heartwood may still be active. 

Another quote from the Wood Handbook is  "The fiber saturation point of wood averages about 30% moisture content, but in individual species and individual pieces of wood it can vary by several percentage points from that value."  Note that they say several points.
Gene - Author of articles in Sawmill & Woodlot and books: Drying Hardwood Lumber; VA Tech Solar Kiln; Sawing Edging & Trimming Hardwood Lumber. And more

Den Socling


drobertson

Lots of numbers for someone who want to build a bar ;D  I think I would have to drop back 15 and punt :D  or, just cut the stock 2x2, kiln it , rip the extra off with the table saw then plane to size, if I wanted to use what I sawed.  Or buy the finish stock and simply build the bar and enjoy 8)  For me building a project, all the facets of it, is what it is all about.  david
only have a few chain saws I'm not suppose to use, but will at times, one dog Dolly, pretty good dog, just not sure what for yet,  working on getting the gardening back in order, and kinda thinking on maybe a small bbq bizz,  thinking about it,

jimF

There seems to be a confusion of terms being used and assumptions in the derivation of the discussed equation.  We have oven-dry( or 0%MC),  FSP ( as stated in both the discussed article and Wood Handbook being ~30%), green moisture content ( which as stated can vary in and between trees) and maximum moisture content.   The assumption that the water has a constant density, no matter which state it is in as it occupies various positions within the wood material comes into play.  The water is in different states within the wood: 1) free which can be assumed to have the density of water as in a drinking glass, 2)vapor similar to vapor in the atmosphere and 3) bound which has a range of density depending on the MC, from 0 to 30% MC( Gene hinted to).  Consider water in a solid state, ice, which actually has many different densities.  There are many different states in which ice can be and still be a solid crystal.  In a similar way bound water can be in a different density depending on the MC because the bond energy is dependent on the the number of water molecules that are between the molecular we are considering and the cellulosic polymere.  Actually, there a a few different theories that have been presented to explain the precise arrangement the water molecules are in but all agree the bond length is shortest at say .01%MC as compared to 25%.

Another assumption in the discussed equation is that the cellulosic polymere do not stay spread apart as the water is lost.  When the water is lost, some voids between the cellulosic polymeres do develop. Both of these facts alter the end result of using the discussed equation.  Also, if there is confusion in the terms for the level of moisture content the equation can be used incorrectly.  Bill Simpson produced a booklet on this subject with extensive tables that is helpful.

To keep this explanation short it was confined to cellulose but to be accurate water does bond with the other constituents of wood.

jimF

Actually, this is related to a topic that is interesting to me!  One can change the apparent color of wood and the dry density of wood by how it is dried.  This is related to drying stresses and voids developing between the constituents of wood as it dries.
1) As Gene mentioned, thin pieces of wood shrink more than thick pieces because the outter shell is stretched as it dries around the unshrunkened wet core.  Then the core is stretched as it dries inside the dry stretched shell.
2)The cellulosic polymere are pulled together as the water is loss as this is what causes shrinkage.  However if the water was replaced by another chemical that forms hydrogen bonds that has a lower bond strength, the force pulling the cellulosic polymeres would be less and more and larger voids would develop.  This can be accomplished by using organic solvent to displace the water, such as alcohol.  Then displace the alcohol with another solvent with even lower hydrogen bond strength.  and finally, let the last solvent to dry off.  This will reduce the density and produce more voids.

Granted, the difference in density will be very difficult to experience, but it will be there.
With the greater number and size of voids in the solvent drying the color will appear to be different than normal drying, lighter in color.  Oak will appear to be almost white.  This is because the light will not be absorbed by the wood material as much but will bounce around in the voids and off the wood.  Similar to polar bear fur is not white but because it is hollow the light is not absorb and bounces around inside and comes out  appearing as white fur.   This is similar to how fiber optics work,  The light reflects off the inside surface of the optic fibers until it comes out the ends.

doctorb

My father once said, "This is my son who wanted to grow up and become a doctor.  So far, he's only become a doctor."

SwampDonkey

From:  FPL -133 (1999) ed. page 3-8



Further on in the paragraph it is only saying that wood dries quicker on the outside. Further on in that edition it shows linear shrinkage as MC% drops from FSP approaching oven dried.  It is impossible to predict how much voids, and size there of as an individual piece dries.

Also, specific gravity changes in wood as moisture is lost from FSP. Even the tables on shrinkage show this for green and 12 % MC.

There is not only confusion, but conflicts in writing. For a lot of it, one has to have faith in the tabulated numbers, not just the math/models. In fact the SP gravity value given for 12 % MC of red pine is actually considered the OD sp gravity by others as I have a note on it. How many more numbers are questionable? Probably a good many, because as I stated earlier the data does not all line up is nice neat lines and curves. (wide standard deviation) ;D

Anyway, all this voodoo makes no difference to the typical portable/back yard sawyer. And I'll stick with my 1/8" per 2" rule when sawing. ;D

Seinfeld must of solved a view problems didn't he. Love that show. :D
"No amount of belief makes something a fact." James Randi

1 Thessalonians 5:21

2020 Polaris Ranger 570 to forward firewood, Husqvarna 555 XT Pro, Stihl FS560 clearing saw and continuously thinning my ground, on the side. Grow them trees. (((o)))

GeneWengert-WoodDoc

Thanks to JimF for pointing out another error in Sebastian's theory and that is the density of bound water.  Indeed many people do not realize that bound water is not a liquid or vapor or solid, so those density values for the three states would not be correct for bound water.

Expanding on several recent posts, the Detroit Redwing - Chicago Blackhawks score is not affected by this discussion.
Gene - Author of articles in Sawmill & Woodlot and books: Drying Hardwood Lumber; VA Tech Solar Kiln; Sawing Edging & Trimming Hardwood Lumber. And more

Den Socling

Gene, I don't understand why you would say that bound water is not a liquid. In a vacuum kiln, I steadily ramp up the heat to overcome increasingly bound water. Humidity in the kiln does not suddenly drop as if there was no liquid water being vaporized. Humidity decreases linearly until I reach the final temperature.

beenthere

south central Wisconsin
It may be that my sole purpose in life is simply to serve as a warning to others

GeneWengert-WoodDoc

It is not a liquid because it does not behave as one.  This is why the heat of evaporation with wood is higher than with liquid water.

Water liquid is two water molecules held together by a hydrogen bond.  With bound water, the water molecule is held to a cellulose hydroxyl group, especially as we get drier; it is not bound to an adjacent water molecule.  The drier the wood, the more and the stronger the wood-water bond.

I do believe the transition is not abrupt but somewhat gradual.

JimF can probably explain it better.

Take a piece of wood under 20% MC (all bound water) and cool it to 20 F or other sub-freezing temperature.  Now dry it.  If the water was a liquid, it would take considerable extra energy for the melting or phase change as the water is evaporated.  But it will not, when it only has bound water.  You cannot freeze bound water.  Of course, once it comes out of the wood, it is now free to behave the way it would as a liquid, etc.
Gene - Author of articles in Sawmill & Woodlot and books: Drying Hardwood Lumber; VA Tech Solar Kiln; Sawing Edging & Trimming Hardwood Lumber. And more

SwampDonkey

I'm more inclined to think these voids in the cells walls are created when free water (water=water) bonds are broken and the water liberated like water evaporating from a mud puddle you now have a void, and the shrinkage is when the water=cellulose bond in the walls are broken and the water liberated.  That volume of bound water lost is the shrinkage. Water as a liquid has to be able to pass through cell walls for them to survive and carry smaller molecules within it for sustenance and maintenance. There are voids in the walls such as bordered pits. A recess in the secondary wall of the cell, open to the lumen on one side and a membrane closing it on the other. There is quite a wide range of temperatures that the density of water changes insignificantly. I believe also this is accounted for when considering the math, there is always base line temperatures to these models, such as 25 C for instance. What it all boils down to, is the complexity limits any reliable precision.
"No amount of belief makes something a fact." James Randi

1 Thessalonians 5:21

2020 Polaris Ranger 570 to forward firewood, Husqvarna 555 XT Pro, Stihl FS560 clearing saw and continuously thinning my ground, on the side. Grow them trees. (((o)))

jimF

Let's see now.  Bound water is on First, free-water is on Second, vapor just got out and liquid is running home.

And following that thought, in my last post I was not specific on what density I was talking about.  As Swampdonkey mentioned "actually considered the OD sp gravity by others", the apparent density or specific gravity changes with MC, which is why the MC at which you are talking about should be included in the explanation. "There is not only confusion, but conflicts" ; confusion yes, conflicts no.  If all the articles are read very specifically you can follow at which MC the sentence is referring to and the conflicts disappears.

The quote:"shrinkage.....continues in a fairly linear manner" is a vague description  "Fairly", yes; exactly no and the curve is a reflection of the varying bond strength and development of voids as the MC decreases.  These voids are not microscopic level like pits, lumens but molecular/polymer level( including the crystalline nature as Gene mentioned).  When mud dries the shrinkage is at the molecular level between dirt and water and the large cracks are the accumulation of the molecular level shrinkage. Yes, for liquid water density changes insignificantly over a large temperature range, but when the state changes is when there is a large density change.  For example liquid/ ice, liquid/vapor and liquid/bound.

In a vacuum kiln, both bound and freewater becomes vapor before or as it comes to the surface.  There is no sudden drop in humidity because 1) the bound water becomes increasingly bonded tighter to the wood as the number of molecules become less and 2) the whole board does not suddenly attain the pressure of the chamber.  I know, I know, everyone says it does, but I cannot envision an experimental setup in which one can seal a sensor in the center of a board to replicate an unopened board in a vacuum setup and really prove the internal pressure instantly reflects the chamber pressure.  So actually during drying, one is seeing an averaging of vapor leaving, liquid evaporating and bound water bonds breaking throughout the whole piece of wood.

When one studies to become an engineer there is one year of course work in transfer of energy & matter and year of course work in thermodynamics (study of energy and changing states of matter).  The systems which they study in those classes are quite simple; they don't involve the structure and chemistry of wood and don't come close to the complexity of what occurs in wood during drying. So hang in there, you're in graduate studies here.

In the end, "for typical portable/backyard sawyer", it may not make a big difference but when you are cutting hundreds of thousands of bdft the difference between 1/8 and ¼ does make a big difference.

Tree Feller

Quote from: jimF on March 03, 2013, 06:38:28 PM
In the end, "for typical portable/backyard sawyer", it may not make a big difference but when you are cutting hundreds of thousands of bdft the difference between 1/8 and ¼ does make a big difference.

I'm a typical backyard sawyer and while it doesn't make a difference, I find the discussion among you experts absolutely fascinating. As you said, this is graduate studies stuff and best of all, it's free.   8)
Cody

Logmaster LM-1 Sawmill
Kioti CK 30 w/ FEL
Stihl MS-290 Chainsaw
48" Logrite Cant Hook
Well equipped, serious, woodworking shop

GeneWengert-WoodDoc

Thanks again Jiim for making clear statements about what I was trying to say.

Your closing statement about graduate level brought back to me the year classes on TRANSPORT PHENOMENA, P-CHEM, and THERMO.  They were tough indeed, especially because all we had was a TI-2500 ($208) which replaced my slide rule.  It could add, subtract, divide and multiply, but did not have a memory.  For big problems, we had punch cards and then stood in line to put them in the computer, only to find out that one card was not right, etc.
Gene - Author of articles in Sawmill & Woodlot and books: Drying Hardwood Lumber; VA Tech Solar Kiln; Sawing Edging & Trimming Hardwood Lumber. And more

jimF

ha, slip sticks (slide rules) nothing like them, fond memories, still have one in the basement.  And punch card readers and main frames, the good old days.  I read an article yesterday comparing 1980 computers to computers today. On 50% of the typical office operations the 1980's computer was faster in accomplishing the task then the bloated current computers.  I guess I aut to stop :D

jimF

It might help in this discussion to realize that the basic different between the various states of any material is the distance between the molecules or atoms and the distance is a reflection of the bond strength between the molecules.  There is no bond between vapor molecules.  There is moderate strength between the liquid water molecules and the same with the distance.  The distance between molecules in ice is very short and the strength very high.  Bound water has a bond strength between liquid and ice and respectively the same with the distance.  The bond strength determines how much energy it takes to break the bond.  With vapor the bond is already broken.  It takes more to break the bonds in bound water than water and even more for ice.
The high bond strength in liquid water as compared to the bond strength between water and the glass is what causes water drops to form on your windshield.  As mentioned earlier  the bond strength within alcohol is low which is why alcohol does not form drop on glass.  In the same way the bonds between alcohol and wood is weaker than wood and water and is why solvent drying reduces the final density of the wood by causing void space by not pulling the wood constituents together as strongly as water does.

beenthere

So...... how does this help answer the question of this thread? Does it change how much pine will shrink in a kiln?
south central Wisconsin
It may be that my sole purpose in life is simply to serve as a warning to others

Paul_H

 :D Beenthere,this is how analysis paralysis can set in and nothing gets done.Reminds me of the time Lloyd Neuman welded up a cast iron manifold for a D8 with a arc welder.It worked and held because he didn't know it couldn't be done.
Science isn't meant to be trusted it's to be tested

isawlogs

Quote from: beenthere on March 03, 2013, 10:40:55 PM
So...... how does this help answer the question of this thread? Does it change how much pine will shrink in a kiln?

:D  Of course it will help, one needs to find an 1980's computer put in all the data calculus algebra and a little of the unknown facts, and then quicker then a laptop opens the answer will pop up.   ::) :D :D

;D
A man does not always grow wise as he grows old , but he always grows old as he grows wise .

   Marcel

Warbird

Quote from: Den Socling on March 03, 2013, 02:49:32 PM
Gene, I don't understand why you would say that bound water is not a liquid.

Quote from: GeneWengert-WoodDoc on March 03, 2013, 03:44:05 PM
It is not a liquid because it does not behave as one.


The Forestry Forum - redefining the Laws of Physics, one tree at a time. 

smiley_eek_dropjaw LOL 

SwampDonkey

Quote from: jimF on March 03, 2013, 06:38:28 PM

In the end, "for typical portable/backyard sawyer", it may not make a big difference but when you are cutting hundreds of thousands of bdft the difference between 1/8 and ¼ does make a big difference.

It doesn't, in two ways. The small sawyer has small volumes and a large  number of customers to satisfy. The customer is much happier with a board he can dry and finish and be assured the dimension he is targeting can be hit. They're not worried about going broke over losing an 1/8" there are other things to worry about. And two on a commercial mill up here at least, shavings off the planer mill is a value added product destined to the pulp mill. This also means a little less sawdust (which is also salable) because of the extra wasteful ;) 1/8" the saw traveled between cuts. The commercial mill also has customers that are even fussier than the back yard sawyer's customers. The models are just not that reliable to give consistent enough results without adding a margin of error, which is this 1/8" your arguing over. You get this curve or line on a graph for dimensional shrinkage and forget that the data is scattered all over the paper. All it does is predict, sometimes it's close, sometimes it way off.
"No amount of belief makes something a fact." James Randi

1 Thessalonians 5:21

2020 Polaris Ranger 570 to forward firewood, Husqvarna 555 XT Pro, Stihl FS560 clearing saw and continuously thinning my ground, on the side. Grow them trees. (((o)))

WDH

As far as pine goes, the effort by industry to squeeze out every ounce of wood has led to high variability in product quality.  As much as 25% of boards in a pack can have marginal use or be unusable.  This more a result of lowering the harvest age and plantation wood versus natural wood than manufacturing, but it all goes together.  Pushing down the green target thickness can at some point lead to more wane, and the grade rules do allow a fair bit of wane.

This situation creates an opportunity for the small sawyer where they are not milling hundreds of thousands of board feet per day.  The small producer, like most of the sawyers on here, can produce a product superior in quality by not pushing the limit like the big commercial mills do. 
Woodmizer LT40HDD35, John Deere 2155, Kubota M5-111, Kubota L2501, Nyle L53 Dehumidification Kiln, and a passion for all things with leafs, twigs, and bark.  hamsleyhardwood.com

GeneWengert-WoodDoc

WDH...good point indeed.  However bad a piece looks, the mill is trying to make a piece of lumber that will be stiff enough (sometimes strong enough, but usually stiffness is the limiting criteria) to function as a joist, rafter, etc.  The piece must be straight enough and have enough nailing surface on the edge, etc. to do the job.  It is so over-designed in most pieces, that it can tolerate some planer skip, and other defects but still do the job.  That is not to say that a few pieces may indeed be off grade.  However, in construction, there is a principle of load sharing, so that one weaker piece has its neighboring piece to help pick up the slack.  I think the "proof of the pudding" is that we do not see roofs or walls collapse with the present lumber and construction techniques.  However, when building we do order more pieces than necessary as we know a few pieces will be thrown away...mostly due to warping after grading.  In fact, that is why engineered beams (like LVL) were able to compete with solid wood floor joists...more expensive but no waste.
Gene - Author of articles in Sawmill & Woodlot and books: Drying Hardwood Lumber; VA Tech Solar Kiln; Sawing Edging & Trimming Hardwood Lumber. And more

isawlogs

 Then should not the grading be looked at differently and make it so that there is not as much waste, seams to me that the stud market grade is full of rejects that twist, bend so much that you basicaly can't use them. It gets veryu frustating to have to buy a pallet load of wood and have a guy sorting the wood needed to build a wall. We cry over made in China, but at times I beleave the big mills are taking a night class on quality from them.
A man does not always grow wise as he grows old , but he always grows old as he grows wise .

   Marcel

GeneWengert-WoodDoc

There are different grades that have different amounts of defects allowed.  The higher the grade, the better the product.

All grading is done at the time of manufacturing.  If a stud is made and graded S-GRN (no drying at all perhaps) then it can be expected to dry and possibly warp after grading.  So, it would be better to get KD19 or KD15 lumber as the maximum MC is 19% or 15%, which minimizes warp after grading because the MC change will be small.

Many of the large stores have their studs inside the building where it is warm and very dry in the wintertime.  So the pieces will dry in the store to a lower MC than they will have in use.  The more we dry, the more warp that we will see.
Gene - Author of articles in Sawmill & Woodlot and books: Drying Hardwood Lumber; VA Tech Solar Kiln; Sawing Edging & Trimming Hardwood Lumber. And more

SwampDonkey

Then in rural areas if you go to the lumber yards of the 'Home Hardware' or the 'BMR's, often the storage area is inadequate and often times some of the piles are just out in the open yard. Someone busts open a bundle and it sits for weeks with the weather raining down on it and it's like fishing lumber out of a bath tub, it's sopping wet. It don't happen a whole lot, but sometimes. Myself, being near a local sawmill, and if I needed building material I would be buying direct. But for a few pieces for a tool shed, not much bigger in floor space than a back yard gazebo or for a picnic table we usually head to the BMR. Sometimes if your not checking, you'll be charged for top grade on the receipt but you had to flip 4 pieces of material for every taker and it wasn't top graded according to the stamp. Most people not in 'the loop' wouldn't know one grade from the other, the stamp means nothing. But they do experience that there was a lot of poor pieces they had to separate out and figured the price is the price. Pricing is another game at retail, there's running foot and board foot.

Also I've been in huge warehouses of kilned dried hardwood lumber. None of those warehouses were heated or climate controlled in any way.

I think we've pretty much circumnavigated the globe on this topic. ;D
"No amount of belief makes something a fact." James Randi

1 Thessalonians 5:21

2020 Polaris Ranger 570 to forward firewood, Husqvarna 555 XT Pro, Stihl FS560 clearing saw and continuously thinning my ground, on the side. Grow them trees. (((o)))

jimF

In the near end it may not make much difference to the small sawyer and to the large producers the waste- sawdust and chips- are of lower value than solid wood, but in the far end it does make a difference.  Gaining knowledge is gaining truth, truth in how God designed the universe.  God created us in His image and with a desire to see Him or know Him.  Moses did not see God's face but he did see his back.  Understanding His work is like seeing Him.  And as the good book says, they will know you are mine by how you love one another.  Well ....they will know you saw knowledge by you being able to predict and explain My created processes.(I know I took liberty here)  I enjoy sharing the knowledge I have gained over the years to those who are interested in gaining understanding - and as Tree feller says: it's free
At least, this is the way I look at life.

SwampDonkey

Facts mixed with statistics and conjecture only gives estimates and predictions that are not always favorable.
"No amount of belief makes something a fact." James Randi

1 Thessalonians 5:21

2020 Polaris Ranger 570 to forward firewood, Husqvarna 555 XT Pro, Stihl FS560 clearing saw and continuously thinning my ground, on the side. Grow them trees. (((o)))

JERICO

Great thread, and "Amen" jimF. 

Sometimes it seems the simplest universal thing is complex because of its design and function juxtaposed against our individual perceptions.
Each tree and each piece of wood is unique and each person is unique, yet there are universal threads that run right through the summation of all.

Now, go build that BAR!! 8)
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Big Axe

fat olde elf

I just knew that this was worth reading all the way through. God bless the Forum......Say your prayers........
Cook's MP-32 saw, MF-35, Several Husky Saws, Too Many Woodworking Tools, 4 PU's, Kind Wife.

Compensation

At this point i don't know if it really matters but i will be cutting them at 1.75".
D4D caterpillar, lt10 Woodmizer, 8x12 solar kiln, enough Stihl's to make my garages smell like their factory :) Ohh and built Ford tough baby!

Gary_C

Quote from: jimF on March 04, 2013, 12:07:11 PM

I enjoy sharing the knowledge I have gained over the years to those who are interested in gaining understanding - and as Tree feller says: it's free
At least, this is the way I look at life.

Well said and thank you for sharing.
Never take life seriously. Nobody gets out alive anyway.

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