Humidity Strikes

[wrjones224]

I live in eastern NC where the humidity shifts drastically day by day. I was upset to arrive to my shop this afternoon and see that the humidity has cause about 15 of my CA finished (not assembled) blanks had shrunk on their tubes. I had just finished them a few days ago on Friday.

It is red oak and I had cut the blanks in a mixture of straight grain, crosscut, and at a 45 degree angle. I find it odd that none of the straight grain blanks had shrunk. I also had about 30 more blanks prepped and they had shrunk as well (none of the them cut as straight grain shrunk).

I know for certain the wood was dry as it came from old hardwood flooring and has been sitting for years. Any tips on how to avoid this in the future? I'm also curious if anyone knows why the straight grain blanks held up more than the crosscut.

 

[jttheclockman]

Crosscut has more open fiber ends than straight grain for one. Same when cutting on a 45 degree angle.

 

[its_virgil]

Wood will be in equilibrium with the ambient relative humidity. Just because the wood has been sitting for years is not an indicator of dryness. Moisture will move in and out of the wood as the humidity fluctuates.

 

[leehljp]

Hoadley's book "Understanding Wood" helped me tremendously. About 40+ years ago, I built a couple of tables, one out of Cherry lumber and one out of Red Oak lumber that had been air dried for about 5 years, and both cracked within a year after building. I asked different people and didn't get much information or help. Then in the late '90s I heard about Hoadley's book and bought it. I read much of it and the most interesting part was how much wood moves in different directions. Some woods do not move at all, Mesquite is one. There are a few others. But then most woods move at different amounts depending upon the species and the specific cut. Hoadley's book will tell you most American woods and how much (percentage wise) these woods move in length, width and depths as they dry.

Do a search on Breadboard ends for a table. Breadboard ends are prependicular to the main boards of the table and most of the time they are Pinned to the long boards and not glued. This allows the breadboard end to expand and contract at a different rate than the longitudinal boards as they expand and contract. Along this same manner, most solid wood table tops (non-plywood) are attached to a table frame using slip joints in a manner that allows all of the wood to expand and contract in different directions without cracking any wood during the wood movement due to heat/cold and humidity swings. The purpose of this paragraph is to show that even expert craftsmen know they cannot fully control nature, but they do come up with methods to deal with it.

As you experienced cross cut and 45° receive the most shrinkage, where as longitude (length wise with the grain) usually shrinks the least. Even many kiln dried woods will shrink and expand in the cross cut types with humidity swings. The one way to prevent this with pens is to learn how to use a good Stabilizer (pressure and vacuum) and let the stabilizer cure before making a pen.

https://www.amazon.com/Understanding-Wood-Craftsmans-Guide-Technology/dp/1561583588/ref=sr_1_1?crid=2LRGOIKFSN158&keywords=understanding+wood+hoadley&qid=1701710960&sprefix=Understanding+wood%2Caps%2C144&sr=8-1

There is one other wood related issue in which wood does not expand or contract like normal wood - when cut/sliced into laminate thicknesses of 1/8" or less and glued onto plywood. But that is another issue.

 

[jrista]

Hoadley's book "Understanding Wood" helped me tremendously.

This right here, is a GEM of a book! I read it, oh, I guess in 2021... Was immensely helpful! One of the best books out there, that really helped me understand what was happening with my wood.

Another gem of a book, not the same author, is "Understanding Wood Finishing" which I bought around the same time. Now, while I read nearly every word of the understanding wood book, I haven't read every word of understanding wood finishing. The latter is a larger book, I think, and so packed with detail. I have read enough, however, to understand finishes much better than I originally did. It has helped me greatly narrow down the number and variety of finishes I use as well...and I guess I've become rather opinionated, too! (Bad side effect, I guess!)

 

[jrista]

Wood will be in equilibrium with the ambient relative humidity. Just because the wood has been sitting for years is not an indicator of dryness. Moisture will move in and out of the wood as the humidity fluctuates.

I think this is a key factor here. Wood settles relative to the ambient humidity. A damp climate near the ocean will leave wood relatively "wet" when its "dry", whereas here in Colorado, wood will shrivel up, wrinkle and can become hard as a rock when fully dry! (What I would give, for my climate to support "some remaining moisture" in my wood, let me tell ya!

I live in eastern NC where the humidity shifts drastically day by day. I was upset to arrive to my shop this afternoon and see that the humidity has cause about 15 of my CA finished (not assembled) blanks had shrunk on their tubes. I had just finished them a few days ago on Friday.

It is red oak and I had cut the blanks in a mixture of straight grain, crosscut, and at a 45 degree angle. I find it odd that none of the straight grain blanks had shrunk. I also had about 30 more blanks prepped and they had shrunk as well (none of the them cut as straight grain shrunk).

I know for certain the wood was dry as it came from old hardwood flooring and has been sitting for years. Any tips on how to avoid this in the future? I'm also curious if anyone knows why the straight grain blanks held up more than the crosscut.

I am curious...did you do anything to seal the ends of the blanks? If I am finishing with CA, I CA the ends of the blank as well, ideally with a very thin, highly penetrating CA glue (i.e. GluBoost Fill n' Finish Ultra Thin comes to mind) so it will get in there a ways, then use a disc sander and pen sanding jig to square it off again (sand to just barely kissing the tube, barely!) Sealing the entire blank, not just the surface grain, can help lock the wood's current moisture content in place (I wouldn't say that's a guarantee, but at the very least it should greatly slow the drying process, which can also greatly limit the amount of wood movement the wood experiences over its lifetime as well.)

Another thing you might try, is to seal the wood with an oil first, before applying the CA glue. I've been experimenting with this myself since I got back into CA finishes (earlier this year, I was exclusively using Pens Plus until another bottle of it went bad long before it was empty...sad consequence of Shellac, I guess!) Some people actually explicitly blend their CA with BLO before applying to their pens, and there is a specific science behind how this creates a new kind of polymer, where the oil and the CA polymers cross-link with each other. CA will bond with an oil underfinish. An oil finish in the wood, could help limit any wood movement that occurs if there IS moisture loss. I would still totally seal the blank in CA, so the above recommendation would stand...this might just help limit wood movement over the LONG term, if it is otherwise impossible to make sure the wood reaches that vaunted "6% moisture" rating, which in a more humid climate, might not actually be possible.

 

[leehljp]

I remember Chris Ledbetter ( aka Chriselle) of Ito-shi, Shizuoka Prefecture, once made a post / thread years ago asking a similar question as in the OP concerning cross-cut. He made and makes excellent pens. He had put one or some in a glass case in the store in which he sold the pens. Sun light came in (and if I remember correctly) shined into the glass case containing the pens, and suddenly there was a big gap in one or a few. Cross grain and 45° will do that. While humidity and temp changes will do that, putting them in a glass case in which sun light shines on or in - and it will magnify the cracks. Very similar to putting a pen on the dash of a closed up car in the summer sun.

BTW, Chris and I were in neighboring prefectures at one time. I sure miss seeing Fuji this time of the year!

 

[leehljp]

Here is a link to a major company with an expensive tool (router bits) that are made exclusively make "slip joints" to allow for wood movement, because wood moves! Even on pens. (But, stabilizing will minimize that.)

Solid Carbide Countersink Slotting Router Bits

Ultra-Shear's new Countersink Slotting Router Bits cut a countersunk pilot hole like you expect from a countersink drill bit…except it can cut sideways, as well as straight in. By feeding laterally you can cut a slot that fits a flathead wood screw and allows expansion and contraction of the...

www.woodpeck.com

 

[wrjones224]

I think this is a key factor here. Wood settles relative to the ambient humidity. A damp climate near the ocean will leave wood relatively "wet" when its "dry", whereas here in Colorado, wood will shrivel up, wrinkle and can become hard as a rock when fully dry! (What I would give, for my climate to support "some remaining moisture" in my wood, let me tell ya!



I am curious...did you do anything to seal the ends of the blanks? If I am finishing with CA, I CA the ends of the blank as well, ideally with a very thin, highly penetrating CA glue (i.e. GluBoost Fill n' Finish Ultra Thin comes to mind) so it will get in there a ways, then use a disc sander and pen sanding jig to square it off again (sand to just barely kissing the tube, barely!) Sealing the entire blank, not just the surface grain, can help lock the wood's current moisture content in place (I wouldn't say that's a guarantee, but at the very least it should greatly slow the drying process, which can also greatly limit the amount of wood movement the wood experiences over its lifetime as well.)

Another thing you might try, is to seal the wood with an oil first, before applying the CA glue. I've been experimenting with this myself since I got back into CA finishes (earlier this year, I was exclusively using Pens Plus until another bottle of it went bad long before it was empty...sad consequence of Shellac, I guess!) Some people actually explicitly blend their CA with BLO before applying to their pens, and there is a specific science behind how this creates a new kind of polymer, where the oil and the CA polymers cross-link with each other. CA will bond with an oil underfinish. An oil finish in the wood, could help limit any wood movement that occurs if there IS moisture loss. I would still totally seal the blank in CA, so the above recommendation would stand...this might just help limit wood movement over the LONG term, if it is otherwise impossible to make sure the wood reaches that vaunted "6% moisture" rating, which in a more humid climate, might not actually be possible.

Thank you all for the insights. It's really interesting to learn about it. I had not put a CA sealer on the ends of the pen in my original post. But I have now. I'm hoping it will help.