Hide Glue Primer #4: Pressing with Hot Cauls

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Recently I was pressing some marquetry that was 26” long. That’s not necessarily a problem with hot hide glue unless your press is only 20” square like mine. Fortunately when I designed my press, I made accommodation for pressing much larger panels than will fit in the press itself by adding the two cheap bar-b-ques on the lower shelf.
Here’s how the whole thing works.

First of all I set out my substrate and marquetry panel and applied hot glue to the whole surface of the substrate, just as I would have if I could press it all at once. Then I placed the marquetry and pressed the top 20”. In the photo below the marquetry is in the press and the last several inches can be seen curling up a little away from the substrate behind the press.

When the glue was sufficiently cured, I removed the piece from the press and heated a 10” x 20” piece of 1/4” aluminium on one of the BBQ’s. If you are wondering why I have two BBQ’s it’s because I also have 20” square cauls. They are 1/2” thick and hold heat longer but this smaller one was all I needed here. You can see the thicker ones a couple of layers below the piece being pressed. The reason you can’t see the marquetry is that the side that is up is covered by the butcher’s paper that it was assembled on. This will be soaked off after the glue has set overnight..

When the caul was hot, I placed it on the unglued end of the piece …….

and pressed it again. The heat of the caul re-liquifies the hide glue and presses it to a perfect flat 100% glued job just as if the glue had been fresh from the pot. It’s worth mentioning that the heating takes about a minute, maybe less. Remember the glue is made from skin. If the caul burns your skin it will burn the glue, so hot to the touch but still touchable is the right temp.

Here you can see the end pressed first sticking out from the back of the press.

This panel became one of the upper doors on my desk.

This is one scenario where hot cauls really pay off, but it is only one. There are many more. For instance any time that you are worried that your glue may have cooled too much to be certain that your glue-up is perfect, you can pop it in the hot press and stop worrying. Also it comes in very handy for flattening veneer. I have two bottles of veneer softener that I have never used because I can flatten just about anything by wetting it with plain water and putting it in the press with hot cauls. when they cool, it’s flat. If it’s still too moist I do it again with some newsprint to absorb the excess. Works for figures and burls and even fragile cupped pieces.

Gotta love that hide glue.

Thanks for looking in.


-- The early bird gets the worm but its the second mouse that gets the cheese.

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Hi Paul, I am planning to get some alu platters very soon and try out them out. It looks like a great way to glue stuff larger than the area covered by my press. A big advantage.

-- Mike, an American living in Norway

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