So what happens below 70 degrees?

[Brett Clark]

I've finally gotten my molds prepared to form some laminated splats for a chair a project. I'm using ProGlue Resin Veneer Bond (http://www.woodcraft.com/Product/2005350/10918/ProGlue-Resin-Veneer-Bond-14-Ounces.aspx?ss=3a332ca1-587d-4515-98b2-6bd32ae741e1) from Woodcraft. According to the instructions 70 degrees is the minimum temperature to use it and as luck would have it, tomorrow is the last greater than 70 day in the forecast for a while(maybe til spring, in Ohio anything could happen). Since my shop is unheated and drafty I'm wondering what kind of problems I might encounter if I go ahead and use it in low to mid 60's.

[Jamie Buxton]

That glue is a urea-formaldehyde. In general, urea-formaldehydes just don't cure properly below their specified temperature range. I can't tell you how much wiggle room that manufacturer builds into their spec, but there's a standard fix: an electric blanket. Put an electric blanket over the piece, and wrap that with a shipping blanket for insulation. I use mine with a vacuum press, so the glue is separated from the blanket by the vacuum bag. If you're using mechanical clamps, you may need do something else -- maybe trash bags. Crank the thing up as high as it will go, and it will raise the temperature of the workpiece quite a bit.

[Brett Clark]

Thanks Jamie. You confirmed what I thought was probably the case. It shouldn't be a problem to get the pieces into a warmer environment once I have them clamped up in the forms. Are fumes much of a problem with this kind of adhesive? I have a space where I can crank the heat up pretty good, but it is fairly tightly enclosed.

[Frank Drew]

Brett,

I know it's partially formadehyde and all, but I've never noticed any noxious fumes with these glues; I used Weldwood's Plastic Resin Glue a fair amount and I can confirm that cold temps when using it can lead to unhappiness, and second Jamie's suggestion to use an electric blanket to keep your glue-up warm if there's no way to heat the workspace.

[Jamie Buxton]

Thanks Jamie. You confirmed what I thought was probably the case. It shouldn't be a problem to get the pieces into a warmer environment once I have them clamped up in the forms. Are fumes much of a problem with this kind of adhesive? I have a space where I can crank the heat up pretty good, but it is fairly tightly enclosed.

Formaldehyde is now considered dangerous. I don't know how much formaldehyde there actually is in a few onces of glue, but I suspect it isn't very much. Despite that, I do try to minimize my exposure. UF takes a long time to cure, so I generally do a glue-up at the end of the day, and leave the shop overnight.

If you're really concerned about formaldehyde, you can shift to epoxy. Like UF, it doesn't creep, so it is good for bent laminations. It also has a long cure time (if you choose the correct catalyst), like UF. One downside is that epoxy is several times more expensive than UF. Another is that uncured UF can be cleaned off tools with warm soapy water, while uncured epoxy is darn difficult to clean up. The epoxy I use mixes up to the consistency of thin pancake syrup, so it makes a nice thin glue layer in the lamination. When I need epoxy, I use West Systems. I get it at a marine supplies store. System Three makes essentially the same stuff. Woodcraft sells one or the other.

[ian maybury]

My experience relates more to epoxies and the like, and i'm no chemist so bear with my crude and very approximate explanations - but it's generally the case that the properties of reactive adhesives dis-improve even if they do seem to cure at lower temperatures - the reason being that you get linking of only a proportion of the reactive molecules as there's just not enough energy about to drive the reaction properly.

Some hardeners go off like an fizzy seltzer, they act as a source of something that triggers the cure reaction. e.g. maybe negative ions. That initial fizz starts on mixing, but runs out because it's over and done long before the cure completes at lower temperatures.

What this means is that it's better not to live dangerously on temperature with reactive adhesives - what looks like a cure may not be what it seems...

ian

[Jon van der Linden]

Regarding epoxies, there is a huge range of products. Without going into brand specifics, there are epoxies that cure very fast and at relatively low temperatures (i.e. lower than common room temp.). There are also a lot of slow ones. Epoxies are temperature sensitive so you do need to check on their temperature range as well. Viscosity is another issue, most flow better at higher temperatures (and cure faster). A few seconds in a microwave give better flow, longer for larger quantities.

Like the formaldehyde glues, you shouldn't breathe epoxy fumes - some are significantly safer than others. Cheap Polyester epoxies are among the worst and are to be avoided.

The electric blanket idea is good, but those don't put out much heat. Much better are either industrial heating blankets, or you can get electric rugs from Japan. For some reason the heating pads and blankets you can buy now put out a lot less heat than the older ones. I bought one two years ago for this purpose and had to return it because it didn't even give off enough heat to keep me warm.

[Myk Rian]

You don't need a lot of heat to keep it warm. An electric blanket is more than enough. Low to medium setting should do it.