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Veneer Tearing Problem2/21
I hope someone will be able to provide some advice of my veneer issue.
I veneered and weighed down the second side just as I did the first side. After I uncovered the second side I was shocked to see that the veneer was split horizontally across the box. This split ran parallel to the grain of the walnut board beneath.
I can only surmise that this split was caused by (1) the thinness of the walnut board and (2) the heat of the HHG. I had to move on so I removed the veneer and filled in all the splits/gaps with a plastic wood filler. I used this filler because it is impervious to water.
After much thought I felt that covering the entire exterior of the box with 1/8” birch ply would allow me to re-veneer the box without further veneer splitting issues.
Again, after much more thought, I began to wonder if using liquid hide glue over the original walnut board would be the better path to follow. Because the heat of the HHG is being avoided, this may allow the veneer to bond to the walnut boards and not split as it did before.
If anyone has any suggestions on how best to proceed, I would really like to hear them.
With all due respect, I think your problem lies between your ears. I have the same affliction. "Analysis to paralysis" is another word for it.
I am currently involved in a few threads here that have 'over-thinking' at their heart. Over- thinking adds steps and materials and may get you nothing in return. It may get you so far from 'home' that you forget your basics.
What would I do with your box? Start over. Make oversize panels veneered on both sides, balanced, as by the book. Dovetail, or miter or however you want to join the panels into a box. The corestock can be plywood or solids, just be sure your grains are going the way they should. Edge band however you like. Rethink HHG. Think veneer press glue, with a rigid glue line. Heck, I'd use epoxy.
I don't think the old eboniste` added veneer to assembled cases unless they had to. One has more control and failure is obvious before the panels are made into a box.
It's not the heat of the glue causing your problem it's the moisture. Every glue up you did added moisture to the core. When the walnut finally dried it shrunk and cracked. I advise against using "veneers" thicker than 1/8" and in your project a simple 1/42" counter veneer would have achieved the purpose of providing a colour matched ground for the face burl. In practice, the pin holes in veneer are filled with tinted pore filler or slurry when sanding and french polishing.
3/16"- 1/4" doesn't act like veneer, it acts like solid wood. I apply re-sawn wood at 3/32" and sand it down a bit after that.
My apologies for the late response, but I have been surrounded by painter and stucco contractors doing repairs to our home.
Thank you very, very much for your detailed response to my query. I now have a much greater understanding as to why the thin walnut boards cracked and ruined my book-matched veneer. Lesson learned.
Because I must complete this jewelry box, I think the best way forward is to overlay the box with the 1/8” birch ply I have prepared and then bond the veneer to the birch ply. I will use screws to align and hold the birch ply in place. All pertinent edges have been mitered so all boards must align precisely. The pre-fitted screws will guarantee this.
I will use Titebond PVA adhesive to bond the birch ply to the box. The birch ply has been dyed with an alcohol solvent dark brown dye. The dye will prevent the light-colored birch ply from peeking through any pin holes in the walnut burl veneer.
I just prepared a fresh jar of liquid hide glue today. I will use this adhesive to bond the veneer to the birch ply. I clearly understand (and respect) your preference for PVA, but I have had great results using traditional hide glue in the past. I brewed the liquid hide glue because (1) I believe it will be as easy to apply as PVA adhesive, (2) will avoid the preparation of traditional hide glue (no glue pot!) and (3) will eliminate the veneer hammering process. And, as you noted, the veneer will have to be pressed firmly in place to insure a good bond and a flat surface when dry. I am prepared for this.
I have no experience with liquid hide glue, so will test my batch thoroughly before I used it on this box.
As before, all comments are welcome.
Your comments and suggestions have been most helpful to me.
It would be faster to just start over. Cut your substrate a little over size, maybe an inch on all four sides. If your worried about pin holes in the veneer, crossband with the same color material or better yet, tint your glue. Press up both sides of your box parts in a vacuum bag. Use unibond 800 and tint it dark. Miter(spline) your box together. Agree with david that you are over thinking this. Hide glue is best used on thicker veneer. If your parts are small you can avoid the vacuum bag and just clamp uniformly.
Your methods are preventing a good project. They have been pointed out to you so you can avoid repeating your mistakes.
"...I must complete this jewelry box" Why? Learning when to drop a path and start over is part of getting grounded in a craft. The box is likely to cause problems down the road. Or as is frequently said "repeating your mistakes and hoping for a different outcome is insanity."
I am surprised by how often people go back to their old, disproven ways even though they asked for help and got it.
It appears that you do not have a fundamental understanding of a proper veneering process, and that your results bear witness to this misunderstanding.
You would do well to study the process a bit further; a good source might be some of the companies that sell the equipment for small scale, vacuum veneering.
You do seem to be consumed with the idea that "I must complete this jewelry box", and decisions made in haste, or under stress, are not always the best ones.
If the jewelry box is a commission that you have already accepted payment for, you may want to see about returning the money and walking away.
If a contract, or ego, is preventing you from doing that, then you may consider having another shop press the veneer for you, so that you can complete your project, and then study the veneering process so that in the future, you will be more successful with your veneering attempts.
Hope this helps.
Your website has a quote that says" Who wants to make the same mistake twice ?"
As for using hide glue with plywood, well that's something I have no experience with and therefore wouldn't recommend. You're combining modern materials with antique adhesives and they may or may not work well together without some experimentation.
Covering what you've done so far with another layer of baltic is just asking for future problems and making your whole glueup more unstable and likely to come apart one day. What's the rush to get the job done, we've all heard the old adage that I don't have time to do it right the first time but somehow I'll find time to do it twice. Start over from scratch, do it correctly.
There are lots of resources available to help people learn veneering, some new books and some old and they all cover hide glue if you are stuck on that as an adhesive, though I question why in todays world you would use it exclusively when there are better, stronger adhesives available. The one reason to use hide glue is for reversibility, which with your current working methods appears to be an important thing. Sorry to sound harsh but your thought processes mystify me.