radiant heat to dry glue

Re: radiant heat to dry glue

Dick Coers

Concentrated heat like that might help make the wood move or crack if not properly kiln dried, instead of setting the glue faster. I'd think you would be better off having the wood in the house overnight, then take it out and do the glue up. I know guys that use an old electric blanket when doing veneer glue ups in the winter. Their shops are warm to work in, but not for setting veneer glue in a timely manner.

agree

Bill Tindall, E.Tn.

What you propose won't work to solve your concern and it may make the wood split or warp.

Have the wood warm and the glue warm. How cold is the shop? If below the chalk temperature of the glue you will have failed joints, because the glue particles will not coalesce into a tough film. This temperature varies with glue type. Read the label.

BTW.....cost to heat

Bill Tindall, E.Tn.

4500 watt equals 4.5 KW. At 20 cents per KW hour that's less than a dollar an hour to run this heater for a glue up. Probably not the most expensive part of your woodworking.

Re: radiant heat to dry glue

TomD

It is amazing what you can get away with by just keeping the glue in a small squeeze bottle in your pants pocket. You want to bring that bottle into your living space so it does not get cold.

Bill is correct about chalking, but you can ignore chalking on the surface of the boards if you are otherwise convinced the stuff in the joint set without chalking.

In the old days they had not well heated shops and got by with hot hide glue. You lob it on thick, rub the edges together. It grabs as it jells and the film is reduced to nothing. You can then paddle the excess back into the pot. The excess glue kept things hot. But there is a stove involved, so they did have a heating source.

Re: radiant heat to dry glue

mike mcnerney

OK I get the picture thanks. How about the radiant heater directly above the cast iron table saw?

Re: radiant heat to dry glue

TomD

I don't see any problem heating it as long as the heat is gentle and balanced side to side, that kind of thing.

Obviously having a thoroughly heated piece, as when the weather cooperates would be best. Baring that, I am not sure what benefit there is to say having the surface of areas that are not near the joint, heated to a minimal depth. Compare that to running a clean iron over the surfaces so that the actual surfaces to be glued would be warm to a slight depth. The glue doesn't penetrate very deeply so you don't need much heat penetration. Things can get tricky when parts you are gluing or varnishing cool off or heat up. Cooling can suck moisture out of the coating, heating does the reverse, it blows air in the wood into the coatings.

I bring stuff into the house.

glue theory-what has to happen

Bill Tindall, E.Tn.

Presuming we are talking about white or yellow glue, for the others work different and have different effects from temperature.....

These glues are a suspension of tiny polymer(glue)balls in water. (BTW, latex paint is the same and "dries" the same. The glue balls are swollen with solvent and mushy. When spread on the wood the water wicks into the wood leaving behind the glue balls. If the temperature is high enough the mushy glue balls coalesce into a film . The solvent in the glue then diffuses away into the wood and the mushy film becomes tough. We say the glue has cured which sums up the coalescing and toughening.

If the temperature is too low the balls don't coalesce. Instead of a tough film between the wood layers there will be a layer of loosely stuck together hard glue balls that are not coalesced into a tough film. The cured glue will have no strength. This phenomena is called "chalking" because the loosely stuck together glue balls resemble white chalk.

The temperature that the glue chalks depends on the details of the glue formulation. Titebond regular must be used above 50 degrees. Extend can be used down to 40 degrees F. These values can be found under "specifications" for any glue.