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General Forestry => Drying and Processing => Topic started by: scsmith42 on October 23, 2018, 08:51:50 AM

Title: Methods for drying freshly sawn veneer?
Post by: scsmith42 on October 23, 2018, 08:51:50 AM
I’ve manufactured a sawn veneer for eight years, but always dried the boards first and then used a precision resaw.  It’s worked great, but I have a customer in a time bind who needs some veneer leaves from a customer’s log within a couple of weeks.  The log is oak crotchwood.

Is there any information available for a small operator regarding drying 1/16” - 1/18” veneer sawn from green logs?  We would be looking at around 1000 square feet, which will probably be made up of around 100 - 200 sheets.  I’m trying to figure out a method that will provide the highest quality but not require me to have to go wild with fabricating closely spaced snickering grates or have an extraordinary amount of labor involved.

A few years back I had a conversation with a guy that milled a lot of tonewoods into 5/16” thick blanks, and I recall that he used grates similar to oven grates in-between his leaves.  They were custom made and basically supported the veneer on 1” centers, or thereabouts.

I’ve read about techniques where several sheets of newspaper were put in between the veneer leaves and the entire stack weighted down, but the newspaper had to be changed daily.  Seems labor intensive to me, plus the concern for the paper to stick to the veneer leaf or the ink to run and stain.

Suggestions and thoughts?

Scott
Title: Re: Methods for drying freshly sawn veneer?
Post by: ljohnsaw on October 23, 2018, 09:28:20 AM
 popcorn_smiley :P
Title: Re: Methods for drying freshly sawn veneer?
Post by: Southside on October 23, 2018, 09:30:38 AM
Would like to see what you find out.
Title: Re: Methods for drying freshly sawn veneer?
Post by: Crusarius on October 23, 2018, 10:30:30 AM
wonder if instead of using a custom made grill you could find a decent fence material that would work? unfortunately it probably would not be very smooth.

I am definitely interested to know the results of this. I just cut some veneer and within a few hours it had already cupped like mad.
Title: Re: Methods for drying freshly sawn veneer?
Post by: curved-wood on October 23, 2018, 02:24:19 PM
Years ago I've sold some 10/4 ash top grade to students that were making chair with very thin laminations around 1/16''. I went to a manufacture that make the thin layers of hardwood that is glued on top of presswood. Not that big company, may be 5 or 6 employees. Doing only the thin stuff and not the presswood part. The ash was heavily steamed, sliced and not sawed and then went throught a dryer. That dryer works like the autofeed on a thickness planer but on the  slow side. The thin layer are feeded in that dryer, move slowly and  comes out at the other end dry. I didn't believe it : drying wood that was steamed in less than a minute without cracks. An  employee even tested in front of me the % of humidity .  So there is some machine that does it. No idea what is the cost and propably hard to find even in the used equipment. Anyway that is a track that could be explored
Title: Re: Methods for drying freshly sawn veneer?
Post by: scsmith42 on October 23, 2018, 04:14:26 PM
Years ago I've sold some 10/4 ash top grade to students that were making chair with very thin laminations around 1/16''. I went to a manufacture that make the thin layers of hardwood that is glued on top of presswood. Not that big company, may be 5 or 6 employees. Doing only the thin stuff and not the presswood part. The ash was heavily steamed, sliced and not sawed and then went throught a dryer. That dryer works like the autofeed on a thickness planer but on the  slow side. The thin layer are feeded in that dryer, move slowly and  comes out at the other end dry. I didn't believe it : drying wood that was steamed in less than a minute without cracks. An  employee even tested in front of me the % of humidity .  So there is some machine that does it. No idea what is the cost and propably hard to find even in the used equipment. Anyway that is a track that could be explored
Good info - thanks.
I've toured a commercial veneer slicing plant, and that's pretty much how they dried it.  But that was also 1/32" veneer and I'll be working with something thicker.
I've been wondering about sandwiching layers of construction paper in-between the veneer leaves, and then weighting the stack for 8 hours or so, and then swapping out the construction paper.
Another thought I've had is to do the same thing, but in a vacuum bag with a vacuum pump attached. 
I have a "JoeWoodworker.com" type setup for vacuum bagging veneered panels but have not tried to use it for drying.  Obviously a vacuum bag system for woodworking would not pull the same vacuum as a vacuum kiln but still might work.  Would probably have to set the bag on top of some heating pads or similar in order to get some heat into the material.
Title: Re: Methods for drying freshly sawn veneer?
Post by: btulloh on October 23, 2018, 05:28:44 PM
I have re-sawed thicker stuff for curved laminated furniture but always from KD stock.  The stuff I sawed was usually thicker than average veneer.  When sawing veneer, I usually sawed a bit over 1/16 up to maybe 1/8.  The few times I sawed something green that thin, it did not want to dry well. I found that working with 1/16" or so veneer was a lot better than using the really thin stuff for most things anyway. 

Commercial flitch-sawed veneer that's been sliced doesn't come flat either.  It doesn't have a lot of checks but there are a few.  You have to get it to relax using a wet towel and an iron right before use it.  

Unless you're going into production, I'd re-saw KD stock rather than trying to get green to behave.  Just my experience with it.  Your mileage may vary.

Interesting to follow this though and I hope it all turns out well. 
Title: Re: Methods for drying freshly sawn veneer?
Post by: GeneWengert-WoodDoc on October 23, 2018, 09:30:17 PM
You can dry it in a room at 80 F with vents to the outside or with a DH in a very short time.  One key is stacking.  Use 12” sticker spacing and then two sheets of veneer, one on top of the other, then stickers, then two veneer sheets, then stickers, etc.

Note that if the grain is not flat, or if there is tensionwood, you will get buckle.  Make sure to saw fairly close to parallel to the bark to help keep the grain straight.
Title: Re: Methods for drying freshly sawn veneer?
Post by: scsmith42 on October 23, 2018, 10:21:44 PM
You can dry it in a room at 80 F with vents to the outside or with a DH in a very short time.  One key is stacking.  Use 12” sticker spacing and then two sheets of veneer, one on top of the other, then stickers, then two veneer sheets, then stickers, etc.

Note that if the grain is not flat, or if there is tensionwood, you will get buckle.  Make sure to saw fairly close to parallel to the bark to help keep the grain straight.
Gene, thanks for chiming in - I was hoping that you would do so.
What I’m milling are some white oak crotch wood logs, so the grain will Definately not be flat!  I typically mill parallel to the pith in order to maximize the quartersawn ray fleck in the middle pieces and to have consistent lengths of crotch grain pattern.
Are there any significant dangers of checking with a 12” sticker spacing on a 3/32” slice of green crotchwood white oak veneer?  Concern for cracks/checks was what was prompting me to dry stack with paper, cloth or cardboard in-between the sheets.  I would think that the drying time would be relatively short.
Considering the relatively thin thickness, is sterilizing even necessary?  Seems to me that at 3/32 any larvae, beetles or eggs would be milled in half.
Title: Re: Methods for drying freshly sawn veneer?
Post by: Tom the Sawyer on October 24, 2018, 12:03:49 AM
Scott,
I had a client for whom I often milled at 1/4 for his lamination projects.  He stacked one board wide, using heavy, corrugated cardboard between layers, with the open ends at right angles to the length of the 'boards'.  He used weight on the stack and a fan blowing perpendicular to the stack.

Tom
Title: Re: Methods for drying freshly sawn veneer?
Post by: GeneWengert-WoodDoc on October 25, 2018, 06:04:10 PM
Checking in oak, that is drying checks, are caused because the surface dries while the core does not.  With thin veneer such as you have, the shell to core difference in MC and shrinkage is very small, so the risk of drying checks is small.  Checks from veneering can develop, sometimes called lathe checks, but they are only on one side of the veneer.

For quartersawn, as you state, you would not saw parallel to the bark, but perpendicular as much as possible to maximize fleck.

Using dry paper products will instantly dry the wood surface which is more likely to check due to a moisture gradient until the paper is wet.  Then the paper and veneer will dry pretty much the same, with the paper making the thin veneer dry as though it was a little bit thicker...more slowly.  As you might guess, slow air speed is important with veneer drying to avoid drying too fast.  Even so, commercial veneer dryers will dry sheets in minutes not hours or days.

Keep in mind that flat veneer is not likely, unless your definition of flat is not very exacting.  With thin veneer, this waviness is ok, as we can press the veneer flat when laminating it to a core.  With thick veneer, we loose flexibility, so "unflatness" can be an issue.

Sometimes when laminating, we will lightly sand the veneer face that will be glued with just one pass.  This gets rid of surface fibers that will not glue well.  Wipe off the dust before gluing..I like alcohol for this wiping as alcohol is a non-wood-swelling liquid...sometimes called NGR (non-grain-raising).
Title: Re: Methods for drying freshly sawn veneer?
Post by: scsmith42 on October 25, 2018, 06:32:31 PM
Checking in oak, that is drying checks, are amused because the surface dries while the core does not.  With thin veneer such as you have, the shell to core difference in MC and shrinkage is very small, so the risk of drying checks is small.  Checks from veneering can develop, sometimes called lathe checks, but they are only on one side of the veneer.

For quartersawn, as you state, you would not saw parallel to the bark, but perpendicular as much as possible to maximize fleck.

Using dry paper products will instantly dry the wood surfacemore likely to check due to a moisture gradient) until the paper is wet.  Then the paper and veneer will dry pretty much the same, with the paper making the thin veneer dry as though it was a little bit thicker...more slowly.  As you might guess, slow air speed is important with veneer drying to avoid drying too fast.  Even so, commercial veneer dryers will dry sheets in minutes not hours or days.

Keep in mind that flat veneer is not likely, unless your definition of flat is not very exacting.  With thin veneer, this waviness is ok, as we can press the veneer flat when laminating it to a core.  With thick veneer, we loose flexibility, so "unflatness" can be an issue.

Sometimes when laminating, we will lightly sand the veneer face that will be glued with just one pass.  This gets rid of surface fibers that will not glue well.  Wipe off the dust before gluing..I like alcohol for this wiping as alcohol is a non-wood-swelling liquid.
Gene, thanks for sharing your insight.
Title: Re: Methods for drying freshly sawn veneer?
Post by: Classic1 on October 28, 2018, 09:56:28 AM
Why not put them in a flat vacuum press table.  I’d think they would dry out perfectly flat within a day like that.
Title: Re: Methods for drying freshly sawn veneer?
Post by: scsmith42 on October 28, 2018, 05:45:00 PM
Why not put them in a flat vacuum press table.  I’d think they would dry out perfectly flat within a day like that.
Unfortunately I don't have access to one.
Title: Re: Methods for drying freshly sawn veneer?
Post by: low_48 on October 28, 2018, 11:41:31 PM
Even commercial high figured veneer will be anything but flat out of the drier. I've used walnut burl that had at least 1/4" high buckled sections. It took some processing in the vacuum bag to make it flat before using. My opinion is that crotch section will really buckle badly in the drying process. Especially if it's white oak. Good luck
Title: Re: Methods for drying freshly sawn veneer?
Post by: scsmith42 on October 29, 2018, 10:07:05 AM
Many thanks to everybody for their input.

I'm planning to mill some later today and try out a couple of different drying methods.  I'll stack and sticker some, stack some with paper in-between the leaves, and put some in a vacuum bag too.  

Should have some results later this week.
Title: Re: Methods for drying freshly sawn veneer?
Post by: btulloh on October 29, 2018, 10:51:13 AM
Thanks for the report.  I'm looking forward to seeing how it comes out.
Title: Re: Methods for drying freshly sawn veneer?
Post by: Sawmill_Bill on September 07, 2021, 09:47:29 AM
Any update on how this worked out for you?

I have a similar project with white oak crotch wood "veneer" slices.  The product will need to be 16" wide and 4' long.  We have the fresh cant and are ready to saw it into thin slices.  Just need to figure out how to dry it.
Title: Re: Methods for drying freshly sawn veneer?
Post by: Sawmill_Bill on September 07, 2021, 11:03:56 AM
Just read the "drying coaster material" thread.  I will look into that method for my project.
Title: Re: Methods for drying freshly sawn veneer?
Post by: metalspinner on September 08, 2021, 07:58:19 AM
Just brainstorming…
Aluminum expanded metal sheets used as spacers could make a fairly rigid, good airflow “sticker” material. Sized to the size of the veneer sheets. 
Title: Re: Methods for drying freshly sawn veneer?
Post by: scsmith42 on September 08, 2021, 10:56:12 AM
Any update on how this worked out for you?

I have a similar project with white oak crotch wood "veneer" slices.  The product will need to be 16" wide and 4' long.  We have the fresh cant and are ready to saw it into thin slices.  Just need to figure out how to dry it.
As Gene advised, Sawn thin and stickered on 12” centers, with low air flow worked well. Because of the grain the sheets distorted a little, but still could be pressed flat during glue up.
Title: Re: Methods for drying freshly sawn veneer?
Post by: Crusarius on September 08, 2021, 05:05:31 PM
I would be leary to use aluminum, I think stainless would be much better. Aluminum likes to oxidize and leave black lines.