Clamping veneer onto speaker face - paper backed & Unibond 800

[andrew whicker]

Hi,

Quick question, to those who have used Unibond 800 on paper backed veneer... (vacuum or mechanical press) do you apply glue to only the substrate or both substrate and veneer?

Cheers,

[John TenEyck]

Same as regular veneer; only the substrate.

John

[Richard Coers]

Why are you going to the expense of 800 for gluing down paperbacked? The bond quality is already set by how good the company glued on the paper. I'd suggest Unibond 100 or even simple Titebond. You don't have a bleed through issues with the paperbacking. I despise paperbacked and it creates so many issues for folks that don't apply the finish correctly. Go with too heavy of coat of a hot solvent finished like lacquer and it can weaken the bond between the paper and the veneer. When I read about veneering issues, the first issue is almost always related to the paper backing.

[andrew whicker]

I'm stuck with paper backed for this project and my unibond will go bad soon...

But yes, agreed and that makes sense.

[Mel Fulks]

Again I suggest the Weldwood type “brown glue “ plastic resin glue. It can be mixed thin enough to drip, NOT stream off stirring stick.
Plenty of working time, you can glue up a big stack of parts at one time . Put plastic, even bags from store purchases between each unit
then put some weight on top.
The glue spreads best after resting 10 or 15 minutes after being mixed .

[andrew whicker]

I'll keep that in mind for next time. May try it out. I normally try to use non paper backed / raw veneer.

I'll probably stick with Unibond products, Titebond III and epoxy (West Systems) for my projects (veneer and lumber). I'm familiarizing myself with a few options and keeping it as simple as possible. I'll be doing the same with finishing techniques... getting a few products down well.

I used Hide Glue flakes for a few veneer projects to get familiarized and I just wasn't happy enough with the results / didn't enjoy the finicky-ness even though I was excited to glue down veneer w/o a press.

[John TenEyck]

Again I suggest the Weldwood type “brown glue “ plastic resin glue. It can be mixed thin enough to drip, NOT stream off stirring stick.
Plenty of working time, you can glue up a big stack of parts at one time . Put plastic, even bags from store purchases between each unit
then put some weight on top.
The glue spreads best after resting 10 or 15 minutes after being mixed .

Weldwood PRG recommends something like 250 psi for bonding. I'm likely wrong, but it's a really high number, far higher than you will get stacking some weight on top. It's also far higher than I can get in my vacuum bag. For that reason I switched from PRG to Unibond 800 which requires only minimal pressure to effect a good bond.

John

[andrew whicker]

Oh, and CA glue with applicator tips just in case I get a bubble... But I swear I didn't just get a bubble or two. If I did I would own up to it.

[Kevin Jenness]

"Weldwood PRG recommends something like 250 psi for bonding"


I think those pressure recommendations are developed for industrial applications like edge gluing staves from a straight line ripsaw. Titebond recommends 175-250 psi for hardwoods, but experience has shown (me at least) that what is needed is enough pressure to get the laminates into contact with a thin, even glueline- usually less than those guidelines. I have had no problems using ppr adhesive with a vacuum press (~10 psi).

[Mel Fulks]

John, I’m sure you are right about all of that. The stacking I suggest relies on good flat material and I think that is likely with speaker boxes.
The thin mix I learned in mill work and was well tested over time by guys who learned the same way I did. It works. It’s contact cement that
needs more rules !

[jerry cousins]

i keep my jugs of unibond in the freezer between glue-ups - lasts a lot longer
jerry

[John TenEyck]

"Weldwood PRG recommends something like 250 psi for bonding"


I think those pressure recommendations are developed for industrial applications like edge gluing staves from a straight line ripsaw. Titebond recommends 175-250 psi for hardwoods, but experience has shown (me at least) that what is needed is enough pressure to get the laminates into contact with a thin, even glueline- usually less than those guidelines. I have had no problems using ppr adhesive with a vacuum press (~10 psi).

I have had no failures with PRG in my vacuum bag either. However, I have proven through unwanted failures with TB glues that you do need some level of pressure to get a good bond, specifically when edge gluing shop sawn veneer to make a panel. You know, you tape up a panel, fold open the joints, run a bead of glue, and then fold the joints shut. I've had two or three of those split open a year or two later on the glued up panel. So the comment that glue is stronger than the wood itself is only true if the mating surfaces are clamped with at least some amount of pressure. But back to glue in the vacuum bag, Unibond 800 is marketed for use in a vacuum bag and "low pressure bonding". PRG makes no reference about use in a vacuum bag, but does state the need for substantial clamping pressure. I've had no failures with PRG on several hundred square feet of panels but Unibond 800 seems like a better option. The current price for PRG makes it an easy choice, too.

John

[Mel Fulks]

Just want to add that the “drips NOT STREAMS “ off stirring stick is only a tad thinner than glue mixed exactly as the directions on the
plastic resin glue.

[Zach Macklin]

I have glued up 100s of full sheets using a vacuum bag setup. Paper back veneer on mdf using original titebond rolled on with a paint roller. Zero failures. With that said, you aren’t going to use a vacuum bag to apply veneer to the edge of a speaker. That’s going to be done with a board and clamps. This isn’t that difficult.