(04-30-2022, 06:02 PM)KC Wrote: I'd think would be difficult to control the 'how much' with Gorilla poly.
A plastic spreader with small notches works well for spreading most glues, including GG. Gorilla Glue is a lot more useful than many give it credit for. It forms a very rigid bond and is waterproof. Cleanup is it's one drawback.
(04-30-2022, 02:56 PM)Bill Tindall Wrote: WoodCentral is broke so I am trying here. We shall see what I can screw up posting....I learned vacuum veneering in the 4 generation Mack Headley Period Furniture shop in Winchester, Virginia. They use white glue for veneering and I have used it for the past 10 years for vacuum veneering without any problems. If the picture is successful it will show an example.
Well, apparently not. No idea how get a picture from desk top to this site. Well....maybe
White glue like Elmer's GlueAll works well for gluing down commercial veneer. I'm not sure I would trust it with shop sawn veneer on plywood or MDF, though. I can tell you from painful first hand experience that products like Better Bond fail with that combination. Why? Because shop sawn veneer behaves more like real wood. It's generally much thicker than commercial veneer and was sawn, not sliced. Together, that makes it a lot more rigid than commercial veneer. In order to keep it stuck to a stable substrate like plywood and MDF you need a really rigid glue like Unibond 800 or epoxy or Gorilla glue. On the other hand, if you want to put shop sawn veneer over a solid wood substrate, white and some yellow glues would be a better choice because both the substrate and veneer are going to expand/contract quite a lot seasonally and they are better suited for those conditions.
As with many things, there is no universally correct choice.
(05-01-2022, 09:53 AM)jteneyck Wrote: White glue like Elmer's GlueAll works well for gluing down commercial veneer. I'm not sure I would trust it with shop sawn veneer on plywood or MDF, though. I can tell you from painful first hand experience that products like Better Bond fail with that combination. Why? Because shop sawn veneer behaves more like real wood. It's generally much thicker than commercial veneer and was sawn, not sliced. Together, that makes it a lot more rigid than commercial veneer. In order to keep it stuck to a stable substrate like plywood and MDF you need a really rigid glue like Unibond 800 or epoxy or Gorilla glue. On the other hand, if you want to put shop sawn veneer over a solid wood substrate, white and some yellow glues would be a better choice because both the substrate and veneer are going to expand/contract quite a lot seasonally and they are better suited for those conditions.
As with many things, there is no universally correct choice.
John
Great info. Curious why is there difference in expansion between sliced and sawn veneer? And to what degree?
(05-01-2022, 09:35 AM)jteneyck Wrote: I read that a lot, but someone forgot to tell the handrail returns I have glued with it. They are still holding strong, some for almost 10 years now.
During Kodak's investigation of cyanoacrylate polymer for various applications it was discovered this monomer made an adhesive that would stick together most anything, including body parts. Kodak tried marketing the adhesive under the brand name Eastman 910. Shelf life unpredictability plagued the product and the patent rights were sold to Locktite. Locktite overcame the worst stability problems, but we still find bottles of this stuff solid as a rock when we try to use it some time after buying it.
I was part of a team investigating adhesive applications. As stated, we found this adhesive was not permanent, with a bond life that depended on temperature and humidity/moisture. An in-depth investigation of the stability of this adhesive can be found in this reference:
Polymer Degradation and Stability (2008) 1–9.
The bond stability of this adhesive may be sufficient for your application. Just beware this adhesive does not have the permanence of adhesives suited for wood.
(05-01-2022, 10:54 AM)Juss1 Wrote:
Great info. Curious why is there difference in expansion between sliced and sawn veneer? And to what degree?
Theoretically, no, for the same wood species. But practically, yes, because sliced veneer is "creped" in the direction it was sliced, which you wouldn't think would affect cross grain properties, but experience shows it must. Shop sawn veneer is sawn so the structure of the wood is not injured during it's production. You can see how robust shop sawn veneer is, even at equal thickness, compared to commercial veneer just by handling them. Shop sawn veneer is rigid while sliced veneer is pretty limp. Just from that observation you can start to understand why shop sawn veneer behaves more like solid wood compared to sliced veneer. And that translates into more force, if that's the right term, as it tries to expand/contract seasonally, so you have to use a glue that will prevent that from happening when gluing it to really stable substrates like plywood or MDF. The commercial veneer, you could use almost any glue with success. That's why it's important to understand all the details when someone says they have no problems with white glue, yellow glue, whatever glue.
(05-01-2022, 09:41 AM)jteneyck Wrote: A plastic spreader with small notches works well for spreading most glues, including GG. Gorilla Glue is a lot more useful than many give it credit for. It forms a very rigid bond and is waterproof. Cleanup is it's one drawback.
John
I've been using GG for years on anything mortise & tenon... but been disappointed once too often using it for anything else. I would expect some foam 'bleed' in very thin veneer.
Hand cleaner with pumice does a good job getting hands clean for folks that don't wear gloves and don't like to use acetone.
(05-01-2022, 01:01 PM)jteneyck Wrote: Theoretically, no, for the same wood species. But practically, yes, because sliced veneer is "creped" in the direction it was sliced, which you wouldn't think would affect cross grain properties, but experience shows it must. Shop sawn veneer is sawn so the structure of the wood is not injured during it's production. You can see how robust shop sawn veneer is, even at equal thickness, compared to commercial veneer just by handling them. Shop sawn veneer is rigid while sliced veneer is pretty limp. Just from that observation you can start to understand why shop sawn veneer behaves more like solid wood compared to sliced veneer. And that translates into more force, if that's the right term, as it tries to expand/contract seasonally, so you have to use a glue that will prevent that from happening when gluing it to really stable substrates like plywood or MDF. The commercial veneer, you could use almost any glue with success. That's why it's important to understand all the details when someone says they have no problems with white glue, yellow glue, whatever glue.
John
I have made numerous pieces where I glued shop sawn veneer onto 13 ply birch or maple plywood. As usual I used white glue. In these cases the veneer was 1/16" or less. I never use MDF so I can not comment on this situation. I never glue shop sawn veneer thicker than 1/16" so I can't comment on this situation either. Two examples are shown, one rift cut curly ash and the other crotch walnut.
(05-01-2022, 06:16 PM)Bill Tindall Wrote: I have made numerous pieces where I glued shop sawn veneer onto 13 ply birch or maple plywood. As usual I used white glue. In these cases the veneer was 1/16" or less. I never use MDF so I can not comment on this situation. I never glue shop sawn veneer thicker than 1/16" so I can't comment on this situation either. Two examples are shown, one rift cut curly ash and the other crotch walnut.
(05-01-2022, 09:35 AM)jteneyck Wrote: I read that a lot, but someone forgot to tell the handrail returns I have glued with it. They are still holding strong, some for almost 10 years now.
John
You have been lucky. Some museums have not been as lucky with segmented woodturnings.
It is bad for a museum display when segments start falling out.
"the most important safety feature on any tool is the one between your ears." - Ken Vick
A wish for you all: May you keep buying green bananas.
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