Bonding veneer to melamine

      Bubbling veneer and contact cement. (Cabinetmaking Forum) May 1, 2003

I am having problems with veneering my cabinet gables. I build the box from 5/8 melamine, then roll contact cement on the gable and the paper backed veneer that has been finished with lacquer. I don't have a spray system. I use a handheld J-roller to press. It looks great for a while, then some bubbling occurs (this may take a week or a year). A hot iron over cloth does not flatten the bubble. I've had this happen with water base and solvent base. Anyone else use this method?

Forum Responses
(Cabinetmaking Forum)
Did you rough up the melamine prior to gluing to give the glue some tooth? Was your contact application 100% and fairly even? Was the contact completely dry prior to lamination?

It sounds like a de-lam but could be from gassing of either the unreleased H2O or solvent or possibly the MDF-based melamine.

You are creating an unbalanced panel with your process and melamine is not a good surface to bond to in the first place. Contact cement and veneer do not go well together. Your finish may penetrate the veneer and attack the contact. Veneer expands and contracts more than laminate, which may break the contact bond. If you absolutely have to have this type of panel, consider starting with a veneered panel and laminating white laminate to the inside to match your melamine. The panel is still unbalanced but you are far less likely to have problems.

I have learned from experience not to use contact cement with veneer if at all possible.
The above idea is a good one if you can use concealed fasteners. Another method I have used is to build the cabinet with 1/2" melamine for the end panel, then use contact cement to apply 1/4" veneered plywood over that. You can pre-finish or finish after assembly. I hand-apply the edgebanding to that end only after the 1/4" panel has been trimmed flush. No worries about the veneer coming off later.

From contributor K:
Handiwood paper-backed veneer has a sheet of instructions that should be in each carton. Two things have to happen: 1. Use enough contact cement to have a gloss show when dry. Generally takes two coats. They claim the bond will probably fail if not enough cement is used. 2. Do not use a J-roller. (They have a little drawing of a skull and crossbones next to a J-roller, trying to get the user to pay attention.) Use a scraping motion to press it down - the edge of a piece of tempered Masonite works well. Make a tool that looks like a 3" or 4" putty knife with the Masonite as the "blade". Break the scraping edge with sandpaper slightly so it doesn't damage the veneer surface. Put plenty of pressure on it and get every square inch.

Following their instructions I've not had any failures and some of these have been in the field for at least 10 years. Lacquer caused no problems.

With melamine, a sand-over to break the shine does the trick. You will need to remove the melamine dust from the surface with a damp cloth. Get all the dust or the bond will probably fail from that.

As far as unbalanced panels are concerned, the veneer has no tensile properties across the grain in such a thin sheet. Along the length of the grain there is miniscule expansion and contraction - not enough to break a good bond. The paper backer is homogeneous and shouldn't cause a bond loss.

Yes, cold pressed adhesives will make an outstanding bond. So will the contact cement if the instructions are followed. Oh, and forget about vacuum bags for contact cement in this application. You will get only about 15 lbs./sq. inch of pressure. With a scraper you can get several hundred pounds/sq. inch.

The posts about using a scraper and making absolutely sure your contact is well into open time are right on. Also be sure to allow 48 hours before finishing. And if you must use contact, consider TAC 357.

Contributor K, are you scraping before or after your veneer is finished?

From contributor K:
The scraping is done before finishing. After pressing ("scraping") the veneer, it's going to need some finish sanding. The only pre-finished veneer I'm familiar with has a phenolic backer like plastic laminate and can be pressed with a J-roller for applying bond pressure.

From contributor P:
Contributor K, are you using waterbase contact cement? Have you tried your method with maple veneer? Do you do much veneering? Vacuum bags and contact cement?

From contributor K:
Contact cement is 3M Fastbond 30 - waterbased. It is brushed on with 4" foam disposable brushes.

This method is specifically for paper-backed veneers - species doesn't matter since the paper/veneer bond was accomplished by the manufacturer.

I only use paper-backed veneers and then only to deal with a special situation such as covering melamine cabinet ends.

A vacuum bag can't provide enough pressure per square inch to bond contact cement - less than 15 lbs. Use vacuum bags for adhesives that cure and form a rigid glue-line.

From contributor P:
Vacuum presses create about 1700lbs per sq ft or 12lbs per sq in. Never thought of using one with contact cement.

I have used your method and I would not recommend it. I have heard that water base is better for wood. But I would recommend the phenolic backed product.

I'm currently in the process of re-veneering a bunch of maple Nbl that was applied with the method you describe. I should also say that Formwood is replacing the veneer at no charge (good company) with a phenolic-backed product they have.

But in the future where possible I'm going to go with the vacuum method. I have not heard of a failure with this method and continue to hear of and experience failures with contact cement.

From contributor K:
I thought that 25 lb./sq. inch was recommended for bonding plastic laminate (has phenolic back) with contact cement. You can get that much pressure with a J-roller but not a vacuum bag.

If you're going to use a glue that cures while under vacuum bag pressure, that will work.

Contact cement fails if not enough is applied to surfaces, surface(s) are dusty or contaminated, it has dried too long, it hasn't dried enough or not enough pressure is applied to create a full bond.

Fastbond 30 has been dependable for me - it has a much higher solids content than the solvent carried cements.

1. Did you use the right kind of roll-on contact? There are spray grades and roll-on grades.

2. *Too much glue* and because of this your thinner base hasn't had near adequate time to evaporate.

3. "Lacquer thinner" (glue) base eeked through the veneer kraft backing, through the veneer and got to your finish causing it to bubble-up (gassing).

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