Crotch Veneer Glue-Ups for Cabinetry
Detailed advice on using crotch veneer to make panels for cabinet construction. July 14, 2010
Question
I am in the process of building 45 42" cathedral wall cabinets. Each will contain a raised panel that I plan to veneer a figured walnut crotch (paperless). I am concerned about two factors.
1: Glue bleed-through while in the press.
2: Glue compatibility with the finish process.
I plan to use an oil based stain and then lacquer sealer and finish coats. Can anyone recommend a good adhesive choice for the veneer given my requirements?
Forum Responses
(Veneer Forum)
From contributor C:
If crotch cut veneer moves, it will crack. PVA is flexible and allows some movement. Urea is a plastic resin material and will not move. Also, bleed through can be controlled by using nut shell flour.
We have no issues with finishing using oil based stain or alcohol based stain (not sure about water based). Our experience is based on making crotch mahogany grand pianos 5-plied using basswood lumber core. Tricky stuff, but we have had few problems using urea glue from Custom Pak.
From contributor P:
I have done a few solid raised panel doors with crotch or burl veneer pressed on both sides. I then ran them through the shaper after pressing to profile without a problem. As mentioned, the veneer will probably split, but the urea will not show when stained (unless the crack is huge). The PVA will show up in all the splits and have to be carefully removed and filled. Trust me, this will not be fun. The urea seems to be invisible after finishing. I have used water aniline dyes, oil based stains and topcoats and have never had a problem.
From contributor B:
Maybe contributor C can confirm, but I was told by a knowledgeable veneer professional to always cross-band a crotch or burl veneer before gluing to the substrate. I am using Unibond 800 for my Makore crotch. I almost ruined some panels when I tried TBII. The kick time is way too short for larger panels and crotch/burl veneers are very brittle.
From contributor C:
Yep. We always use poplar x-banding. It locks the grain movement.
From contributor P:
If memory serves me, I made 2-ply cross banded veneers for the curved raised panels we did, but just glued the veneer right to the flat raised panels. I think the agreement was that all the layers moved in unison. Veneer-solid-veneer. I do know that there was never any problem or movement in service. The only objection we had with the 2-ply was the thicker edge seemed more pronounced.
From contributor C:
It's not a good idea to put veneer over solid wood without a cross band. It is almost 100% certain to crack. If you have a museum-like environment with constant humidity control you can do just about anything (that is the case with The Smithsonian). If you look at antiques, you will see the result of not using crossbands (and the down side of using hide glue).
From the original questioner:
Thanks a lot for the replies. When you mention cross band, are you referring to another piece of veneer underneath 90 degrees to the face veneer?
From contributor C:
Yes. Usually something softer and a bit thicker; we use 1/24 rotary poplar.
From contributor P:
Correct. Cross banding is 90 degrees. When I do figured veneers, I have the 2 plies cold pressed flat first, then lay them up. You could feasibly do everything all at once, balancing the panel, but that would be a lot of glue and time would be against you if you are not set up to do so.
Contributor C, yes I am fully aware of the perils of not cross banding. It was some time ago, and it seemed like a workable plan. The veneers were maple burl on a 1.25 thick raised panel. I did see them after 5 years and there were no cracks, crazing or any signs of movement. Lucky, probably. Could be that the burl was more forgiving due to the random grain.
From contributor B:
Yes. Be sure to look at the stock widths before you order the cross band material. Sounds like you have some good sized panels to produce and if the stock is narrow and you are taping the panels, the cross banding can be a bit tedious. Are you familiar with flattening the face veneer material?
From contributor B:
As I was cross banding yet more panels, I was thinking about this process. I was hoping someone might clear this up for me.
I am using an MDF substrate and Unibond 800. I haven't questioned the cross banding idea before, but this project is taking a bit more time than I like, so I got to thinking. I suppose the idea is that when you cross band directly to a straight grained backer, it is more likely to compress the difficult fibers into the backer than if it were directly applied to the MDF. With a rigid glue such as this that also gaps not too bad, it seems very cautious. I understand many of the antiques with intricate marquetry used fish glue adhesives that are susceptible to moisture and do not provide the same bond strength. Just curious to understand this a bit more.
From the original questioner:
I think that the flattening process involves first letting the face veneer acclimate to the same temp as the substrate. Then a conditioner is applied to the veneer and it is lightly pressed to be as flat as possible (a day or two). Then it is ready to be applied?
From contributor B:
The softening description that a fellow veneer pro offered me is below. I will add that on a recent project I was doing using a four way crotch match, I decided to make the end matches after cross banding. Big mistake. Between the time it took to get the stock prepped and back in the bag with the substrate, the two ply curled so much it was incredibly hard to get the sandwich to work and in fact I ended up with a small patch where the stock wrinkled due to this error.
Step one: softener. gf20 I assume? Whatever softener you're using, put it in a spray gun and apply it that way. Saturate both sides. The directions say to dilute, but I use it full strength. Next, separate each piece with paper, making sure to alternate the leaves with the high low valleys opposing each other.
Put the sandwich in the press and pull a half vacuum for about a half hour. After the half hour, pull a full vacuum. While you're waiting for the magic to happen, start laying up for a two ply. Any crotch species should always be two plied. If you don't, you'll wish you did.
After about 8 hours, pull the sandwich out and remove the paper and replace with new paper. Your veneer should be dead flat but still a little moist, so you still need to extract some moisture.
After about two more hours you can take the sandwich out and discard the paper. At this point you have about a 12 to 24 hour window before the veneer starts to lose its magic and goes back to its original shape.
Because the wood fibers have been plasticized, trimming is rather easy, so I would trim the joints and get the face veneer ready for layup on the secondary veneer. Instead of two hole white tape, I'd use no hole brown tape.
Once your face veneer is ready, spread glue on the secondary veneer, apply the face veneer, and back in the bag she goes.
Plain sliced mahogany or poplar works well as a secondary veneer. The less grain, the better. If there are any splits in the feather portion of your veneer after you soften it, you will want to tape those closed as well before two plying.
From the original questioner:
Thanks for the info. You suggest it is important to employ a 2-ply approach when working with crotch veneer. Do you mean to use an additional no-paper backed veneer 90 degrees to the face? So essentially the face side of the substrate would consist of 2 non-paper veneers the crotch (visible) sandwiched with a secondary close grain 90 degrees. These two are then applied to the substrate? If I am correct, could not all 3 be put in the bag at the same time?
From contributor B:
I don't think most do it all at once. Take a read of contributor P's earlier post.
From contributor E:
As far as bleed through goes, I use a bit of Titebond fluorescent glue in the mix. It doesn't take much, and you can see any bleed with a black light immediately, and go at it with a card scraper.
