Darryl Keil Last Activity 2025-09-09 11:09 AM
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Sam Gregerson

 
Subject : veneers cracking after three weeks
Posted : 2002-04-30 2:00 PM
Post #29099
I have had two tables with veneered tops come back from a gallery in the Portland OR area. Both tables were in the gallery about 3 weeks when cracks began to appear. Another table was sold within a few days and has experienced no trouble. A fourth table is at a second gallery in the same general area, no problem.I'm veneering over 3/4" baltic birch using gorilla glue. The first table was of crotch walnut and was most probably 12% moisture content so I therefore accept that to be the fault. The second table I took special care to condition every thing to 6% but again cracks appeared in the African mahogany veneer after three weeks in the gallery. I sponge with water on the baltic birch and then vacuum press until the glue has hardened on a sample.(usually about 1-1 1/2 hrs.)I know this sounds like a moisture problem but what is baffling to me is why I'm having these problems only with this one location and in this time frame. I live in N. Calif. where equilibrium moisture is 12-14% but I can condition material down to 6%. My question is what relative humidity levels can I safely expect to send items to? Am I missing something else?



 
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Darryl Keil

 
Subject : veneers cracking after three weeks
Posted : 2002-04-30 8:07 PM
Post #29102 - In reply to #29099
Dear Sam,What I am surprised at is you having two tables that did not check. At 12 to 14% relative moisture in your area you do not need to wet your substrate at all to get a polyurethane glue to set. I believe the addition of water to your substrate is the real problem although having a low moisture content for the veneer is a good idea or at least good insurance. Let the panel stay in the press overnight as not adding water will take the glue a lot longer to set.SincerelyDarryl Keil: I have had two tables with veneered tops come back from a gallery in : the Portland OR area. Both tables were in the gallery about 3 weeks : when cracks began to appear. Another table was sold within a few : days and has experienced no trouble. A fourth table is at a second : gallery in the same general area, no problem.: I'm veneering over 3/4" baltic birch using gorilla glue. The first : table was of crotch walnut and was most probably 12% moisture content : so I therefore accept that to be the fault. The second table I took : special care to condition every thing to 6% but again cracks appeared : in the African mahogany veneer after three weeks in the gallery. I : sponge with water on the baltic birch and then vacuum press until the : glue has hardened on a sample.(usually about 1-1 1/2 hrs.): I know this sounds like a moisture problem but what is baffling to me : is why I'm having these problems only with this one location and in : this time frame. I live in N. Calif. where equilibrium moisture is : 12-14% but I can condition material down to 6%. My question is what : relative humidity levels can I safely expect to send items to? Am I : missing something else?




 
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Larry Root

 
Subject : Darryl: a followup question
Posted : 2002-05-03 6:14 AM
Post #29109 - In reply to #29102
Darryl,An expert I'm not -- but thanks to your help I've completed one veneered piece. A high MC core would shrink when drying but I'm suprised that a plywood sheet would move enough, I'm thinking this would only be 1-2%, to disturb the veneer (grin, a little knowledge is a dangerous thing). Thus, my question: If the high MC core shrinks and the dry veneer expands, wouldn't the veneer buckle or just crush itself? Why would the veneer or finish crack?Thanks for a very informative site.Very Respectfully,Larry Root




 
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Darryl Keil

 
Subject : Darryl: a followup question
Posted : 2002-05-04 9:41 AM
Post #29111 - In reply to #29109
Dear Larry,You right that the veneer core is not going to expand much but my thoughts are that the veneer will from the excessive moisture sprayed on the substrate that ends up transfering into the veneer. Its during the drying phase that the cracks appear due to shrinkage of the veneer.With all that said I would like to take this oportunity to say that forums in general are flawed in that they dont give people a chance to have a real dialog.Its in this dialog that enough back and forth questions get asked to get the bottom of whats going on. I cant tell you how many times I have been talking over the phone with someone and have them say something off the cuff which turns out to be the real problem, and thats even with a good dialog. Internet forums just dont allow this kind of process, not unless your going to spend endless hours back and forth which can take days. Its not to say they are not valuable and dont offer real benifits, obviously I think they do as Ive taken the time to create and host this one. In the case of the cracking veneer I only have the information he has given me to go on, it could be something entirely different that he may not even have thought to mention or realize he is doing. I would need a good phone dialog to cover all the bases to be sure we were on the right track. So with all this dribble in mind who knows if adding water to the substrate is the core problem, although it definately isnt a good idea and could be the real problem.SincerelyDarryl Keil: Darryl,: An expert I'm not -- but thanks to your help I've completed one veneered piece. : A high MC core would shrink when drying but I'm suprised that a plywood sheet would move enough, I'm thinking this would only be 1-2%, to disturb the veneer (grin, a little knowledge is a dangerous thing). : Thus, my question: If the high MC core shrinks and the dry veneer expands, wouldn't the veneer buckle or just crush itself? : Why would the veneer or finish crack?: Thanks for a very informative site.: Very Respectfully,: Larry Root
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