Pre-Cat Lacquer problem - Woodworking Talk

CabinetGuy · 04-20-2009, 05:55 PM

I'm having a problem with veneer lifting in spots and the finish splitting from it also, but only in spots and only sometimes.
I'm using Weldwood flammable contact cement by Dap and most of my problems have been with 10 mill paper back veneer. I'm finishing with Sherwin Williams Dull Rubbed Pre-Cat Lacquer, using it as it's own sealer, applying 4 sometimes 5 coats. I thin the pre-cat down about 25% so the coats aren't real thick.
I'm thinking that pre-cat is somehow dissolving the contact cement, but I'm only guessing.
Has anybody had or heard of this problem before??
Would a vinyl sealer help prevent it??
I've been doing woodwork for 25+ years and have stuck miles of laminate with the same glue without any problems. Have also stuck miles of veneer and finished with regular nitrocellulose lacquer without the problem. I don't know what's going on,

please help!

Thanks in advance.

Rick Mosher · 04-20-2009, 08:41 PM

Sorry, but I am of the school that contact cement should never be used for veneer work. It should always be hard glued in a press, vacuum bag, hammered or even ironed on. How big is the piece you are working on?

Julian the woodnut · 04-20-2009, 09:10 PM

You don't use contact cement for veneer, period. Especially when you're using laquer. The solvent in laquer will loosen up the contact cement, and cause delamination.

CabinetGuy · 04-20-2009, 09:49 PM

WOW,
I've been doing it for years and years, and have never had a problem with delamination until I started using pre-cat.

cabinetman · 04-20-2009, 09:55 PM

Quote:

Originally Posted by CabinetGuy

I'm having a problem with veneer lifting in spots and the finish splitting from it also, but only in spots and only sometimes.
I'm using Weldwood flammable contact cement by Dap and most of my problems have been with 10 mill paper back veneer. I'm finishing with Sherwin Williams Dull Rubbed Pre-Cat Lacquer, using it as it's own sealer, applying 4 sometimes 5 coats. I thin the pre-cat down about 25% so the coats aren't real thick.
I'm thinking that pre-cat is somehow dissolving the contact cement, but I'm only guessing.
Has anybody had or heard of this problem before??
Would a vinyl sealer help prevent it??
I've been doing woodwork for 25+ years and have stuck miles of laminate with the same glue without any problems. Have also stuck miles of veneer and finished with regular nitrocellulose lacquer without the problem. I don't know what's going on,

please help!

Thanks in advance.

Solvent based contact cement works very well with paper backed veneer. The veneer manufacturers recommend it. If you are brushing or rolling the glue, you may have heavy areas. Spraying the glue works best.

A few possibilities. You may have areas that are glue heavy and didn't flashed off sufficiently. You may have some areas that don't have a matched area for glue (no glue, or not enough). You may have trapped some air. Can't tell where you are located, but if overly humid, the glue flashing may have drawn some condensation. You may have laid a lacquer coat too heavy which allowed the solvent to penetrate to the glue line. I always use a sanding sealer when using lacquer over veneer.

Try letting the glue dry longer. That glue can feel bone dry and still stick good. If you can spray a good thin coat on both pieces, and give it at least 45 minutes to an hour or more (depending on the weather and temperature) it may work better. If you are using the lacquer as a sealer and thinning, that is more vapor intensive than a sanding sealer. The first few coats try spraying tack coats.

Just a note here, that I've gone to waterbased polyurethane for most film finishes. IMO, it's equal to or better than lacquer. I'm pretty tired right now, and I may have forgotten some points.

CabinetGuy · 04-20-2009, 10:28 PM

Quote:

Originally Posted by cabinetman

Solvent based contact cement works very well with paper backed veneer. The veneer manufacturers recommend it. If you are brushing or rolling the glue, you may have heavy areas. Spraying the glue works best.

A few possibilities. You may have areas that are glue heavy and didn't flashed off sufficiently. You may have some areas that don't have a matched area for glue (no glue, or not enough). You may have trapped some air. Can't tell where you are located, but if overly humid, the glue flashing may have drawn some condensation. You may have laid a lacquer coat too heavy which allowed the solvent to penetrate to the glue line. I always use a sanding sealer when using lacquer over veneer.

Try letting the glue dry longer. That glue can feel bone dry and still stick good. If you can spray a good thin coat on both pieces, and give it at least 45 minutes to an hour or more (depending on the weather and temperature) it may work better. If you are using the lacquer as a sealer and thinning, that is more vapor intensive than a sanding sealer. The first few coats try spraying tack coats.

Just a note here, that I've gone to waterbased polyurethane for most film finishes. IMO, it's equal to or better than lacquer. I'm pretty tired right now, and I may have forgotten some points.

Thanks Cabinetman, at least you didn't answer me like I was a stepchild.
I spray the contact with a pressure pot and get good coverage, the humidity is low here in the dry desert. I'll try lighter coats and longer dry time inbetween.
I'll have to chat with you another time regarding the waterbase poly.
Thanks again.

Rick Mosher · 04-21-2009, 01:24 PM

I have worked in two of the best veneer shops in the country and both of them had contact cement available for plastic laminate jobs. Neither of them EVER used contact cement for veneer, paper backed, foil backed or whatever back. Even though it would have been much faster and easier to do so if it were "just as good". The simple fact is that contact cement never dries completely. To be stable veneer should be hard glued. There are many shops who use it and I have worked for a few of them. It seems like I was always trying to fix bubbles and checks all the time. It just doesn't happen in shops that hard glue.

CabinetGuy · 04-21-2009, 05:06 PM

Quote:

Originally Posted by Rick Mosher

I have worked in two of the best veneer shops in the country and both of them had contact cement available for plastic laminate jobs. Neither of them EVER used contact cement for veneer, paper backed, foil backed or whatever back. Even though it would have been much faster and easier to do so if it were "just as good". The simple fact is that contact cement never dries completely. To be stable veneer should be hard glued. There are many shops who use it and I have worked for a few of them. It seems like I was always trying to fix bubbles and checks all the time. It just doesn't happen in shops that hard glue.

I don't think anyone said anything about it being just as good.
All I asked was what was causing it. I didn't ask whether it was right or wrong.
Geeez, is it this hard to get a little help without being belittled?
Maybe instead of telling me this you could have recommended some types of iron on adhesives or maybe told me about the vacuum bag process and how it works.
It's obvious I am doing something wrong isn't it? If it was working I wouldn't be here now would I??
Thanks, but from the response I've seen here already with the exception of cabinetman, who at least tried to help, I don't think I need to participate here.
Lovely board you all have, please note the sarcasm!!
Seeeee Ya

Rick Mosher · 04-21-2009, 08:56 PM

I'm sorry you feel that way Cabinet Guy. I did ask how big of a piece you were working on and never received a reply. It is difficult to give advice when you don't know whether someone is working on a set of cabinets or a humidor. I did have some suggestions depending on what the project was. As to the second reply that was more to cabinetmans response of

"Solvent based contact cement works very well with paper backed veneer."

That is what paper and foil backed veneers are for but I still would not use them.
The proper use of a vacuum bag would probably be great info if you have one but it isn't going to help with the problem you have now. Again I am sorry if my reply offended you in any way and I hope you don't leave a perfectly good web site just because of that.
I would love to try and help you out, just post some more info and maybe even some pictures.

CabinetGuy · 04-22-2009, 12:21 AM

Quote:

Originally Posted by Rick Mosher

I'm sorry you feel that way Cabinet Guy. I did ask how big of a piece you were working on and never received a reply. It is difficult to give advice when you don't know whether someone is working on a set of cabinets or a humidor. I did have some suggestions depending on what the project was. As to the second reply that was more to cabinetmans response of

"Solvent based contact cement works very well with paper backed veneer."

That is what paper and foil backed veneers are for but I still would not use them.
The proper use of a vacuum bag would probably be great info if you have one but it isn't going to help with the problem you have now. Again I am sorry if my reply offended you in any way and I hope you don't leave a perfectly good web site just because of that.
I would love to try and help you out, just post some more info and maybe even some pictures.

No problem Rick, It was Julian's post that ticked me off. I thought it was rather rude and offered nothing, You were just caught in the middle of my attitude.
No offense was taken and I'm sorry I came off on you like I did.

I realize now that the lacquer is deteriorating the contact cement.
When you've been doing something your whole life and it has worked there was never reason to change. I've never been taught or worked for anyone else so all I know is what has worked for me in the past. Now that I am having problems I am searching out the right way to remedy the problem, and am trying to learn the proper methods.

80% of everything I do is commercial. Mostly store fixtures, POS counters type of cabinetry. Stuff that is tore out and thrown away after 5 years so it's not like I have been building heirlooms.

I know how to search the web and I will start looking for other methods on how to apply my veneers.
Thanks, and sorry for the trouble.

scribbles · 04-22-2009, 01:33 AM

Just make sure to use a good respirator, the first time I used pre cat I got high as a kite. It was not fun.

Rick Mosher · 04-22-2009, 01:25 PM

One way to use contact cement in your situation would be to use 1/8" door skins instead of paper backed veneer. That way the veneer has already been pressed and is stable. Just apply the door skin using your contact cement and there will be no bubbles no matter what you finish it with. This may not work for all situations so another alternative if you don't have a vacuum bag would be to apply yellow glue to both pieces and let dry. Then using a hot iron bond them together. This will work for small pieces, I wouldn't want to do it on a counter top or something. The last method would be hammer veneering using hide glue and a veneer hammer. You can do just about anything this way without a huge investment.

scribbles · 04-22-2009, 09:47 PM

That is what I do, I never really experimented with, or was taught how to use vaneers, i always just use 1/8" and contact cement out of a sprayer, it has worked great for years.

Bob Wingard · 04-23-2009, 12:22 AM

I would have to assume that at least one of the following conditions has occurred :

A change in the manufacture of your contact cement ..

The solvent in your pre-cat is compatible with the contact cement .. that is .. the solvent will re-amalgamate the contact cement, causing it to let go ..

First coats of pre-cat are a bit too heavy, leaving the surface wet with solvent for too long, allowing it to react with he solvent ..

Veneer is being cut a bit thinner, allowing the solvents to mingle & react ..

Since alcohol is NORMALLY not reactive with MOST contact cements, I would try a wash coat of 1# cut shellac to seal the veneer's surface. Rule of thumb is usually that shellac will stick most everything .. and most everything will stick to shellac.

Another possibility would be to thin your lacquer with a faster drying thinner if you are in an area with low humidity. The faster you can get the solvents to flash off, the less likely you will be to have the interactions you described.

eeprof · 04-24-2009, 01:48 PM

I restore a good number of vintage wood radio cabinets most of which use veneer which is necessary to replace frequently. I use a latex contact cement with good success. I only use lacquer based finishes but use a vinyl lacquer based sanding sealer which seems to increase leveling and adhesion. I have used many sanding sealers but prefer the Coronado vinyl. I also spray hot (125 degrees) and use no more than 10% solvent thinner.
Tom.