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Hide Glue for Beginners #5: Pressing with Hot Cauls

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Blog entry by shipwright posted 06-13-2013 06:49 AM 1718 reads 3 times favorited 15 comments Add to Favorites Watch
« Part 4: A Little Hammer Veneering Video Part 5 of Hide Glue for Beginners series Part 6: Perfect Splined Mitre Joints in Five Minutes Without Clamps »

Today 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 applied 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 them 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 over night.

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 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.

Paul

-- Paul M ..............If God wanted us to have fiberglass boats he would have given us fiberglass trees. http://prmdesigns.com/



15 comments so far

View Sodabowski's profile

Sodabowski

2039 posts in 1520 days


#1 posted 06-13-2013 07:14 AM

A-ha! so you have a better modus operandi that I do for flattening veneer by means of water and heat – maybe is it the local water that makes a difference, here in Paris, Frogland we have the crappiest tap water around (full of carbonates).

I’ll keep this Al plates idea aside and see if it can be mixed with a vacuum press. Thanks for the tip Paul :)

-- Holy scrap Barkman!

View stefang's profile

stefang

13273 posts in 2021 days


#2 posted 06-13-2013 08:49 AM

Looks like an excellent way to work the hide glue Paul. I’ll have to see if I can find any aluminum plates and BBQ grills. I wonder if the plates can be heated enough with a heat gun? More work, but I’m not sure I can find grills like that here. I suppose smaller plates could just be heated in the kitchen oven. Thanks for this great blog.

-- Mike, an American living in Norway.

View SPalm's profile

SPalm

4845 posts in 2569 days


#3 posted 06-13-2013 10:23 AM

You had me at veneer flattening. Hmmm.
Thanks Paul.

Steve

-- -- I'm no rocket surgeon

View Jim Jakosh's profile (online now)

Jim Jakosh

11729 posts in 1792 days


#4 posted 06-13-2013 11:42 AM

Very neat setup, Paul!!

-- Jim Jakosh.....Practical Wood Products...........Learn something new every day!! Variety is the Spice of Life!!

View nomercadies's profile

nomercadies

518 posts in 1026 days


#5 posted 06-13-2013 01:44 PM

Do you have information on making the press? Looks like something a person could use for several different processes.

-- Chance Four "Not Just a Second Chance"

View Greg..the Cajun  Box Sculptor's profile

Greg..the Cajun Box Sculptor

5178 posts in 1995 days


#6 posted 06-13-2013 02:06 PM

Paul…I never do any veneering…but I look at your techniques and work and always get amazed in such a good way…!

-- We all must start somewhere in our journey of doing what we love to do.

View shipwright's profile

shipwright

5084 posts in 1485 days


#7 posted 06-13-2013 03:12 PM

nomercadies, You can find the press in my projects here.
I use it every day for all sorts of things. Most of the details you need are in the project post photos. I have more photos if you need them.

-- Paul M ..............If God wanted us to have fiberglass boats he would have given us fiberglass trees. http://prmdesigns.com/

View Karson's profile

Karson

34891 posts in 3087 days


#8 posted 06-13-2013 05:26 PM

Paul: Using the heated plate, how long does it take to heat the glue and then loose enough of the heat to break everything down.

-- I've been blessed with a father who liked to tinker in wood, and a wife who lets me tinker in wood. Southern Delaware karson_morrison@bigfoot.com †

View shipwright's profile

shipwright

5084 posts in 1485 days


#9 posted 06-13-2013 06:18 PM

It.depends on the thickness of the plate. Cool to touch is a good indicator. I would usually leave the 1/2” cauls a few hours at least. I also have 1/8” ones that I use a lot more often and they will usually be cool enough in an hour or so.
That said it’s always best to leave it longer.

-- Paul M ..............If God wanted us to have fiberglass boats he would have given us fiberglass trees. http://prmdesigns.com/

View Lee A. Jesberger's profile

Lee A. Jesberger

6663 posts in 2667 days


#10 posted 06-13-2013 08:29 PM

Very nice setup, Paul!!

-- by Lee A. Jesberger http://www.prowoodworkingtips.com http://www.ezee-feed.com

View Mauricio's profile

Mauricio

6841 posts in 1839 days


#11 posted 06-13-2013 09:39 PM

Great tip Paul, thanks for sharing.

-- Mauricio - Woodstock, GA - "Confusion is the Womb of Learning, with utter conviction being it's Tomb" Prof. T.O. Nitsch

View grizzman's profile

grizzman

7095 posts in 1990 days


#12 posted 06-13-2013 10:07 PM

now come on Paul, admit you stick some steaks down there and it inspires you to work harder, but if they also help with your woodwork, then what a good deal…your a pretty smart guy, i always love seeing what you show us in ways of getting something done when there is a challenge , oh and by the way, if i happen to come by, i like my steaks medium rare..mushrooms and onions also…:)

-- GRIZZMAN ...[''''']

View Joe Lyddon's profile

Joe Lyddon

7799 posts in 2739 days


#13 posted 06-14-2013 01:15 AM

COOL lil BBQ Press you have there…

You could make a hamburger mold… press’em… yep… cook’em too… LOL

That a nice wood gluing press too… I can see how you could put longer pieces for top/bottom with work between and cauls on the outsides to get more out of the press…

Nice COMBO…

-- Have Fun! Joe Lyddon - Alta Loma, CA USA - Home: http://www.WoodworkStuff.net ... My Small Gallery: http://www.ncwoodworker.net/pp/showgallery.php?ppuser=1389&cat=500"

View BigTiny's profile

BigTiny

1664 posts in 1575 days


#14 posted 06-20-2013 01:12 AM

For longer pieces that aren’t TOO much longer than the press, why not use longer pressing cauls and use clamps on the outer ends?

Paul

-- The nicer the nice, the higher the price!

View BigTiny's profile

BigTiny

1664 posts in 1575 days


#15 posted 06-20-2013 01:24 AM

To Stefang:

A heat gun would work, but the trick would be keeping the heat even over the entire piece.

A better idea is to measure the oven racks in your stove and have cauls made that will fit in it. Leave about an inch or two space around the edges for heat to travel around the oven. Set it for 200 F and then let cool until it is hot to the touch but not too hot to handle, then use.

Heated cauls are also great for fixing “oopses” in veneering as it will loosen pieces so you can reposition them. Use a caul just large enough to cover the area you want to fix.

Paul

-- The nicer the nice, the higher the price!

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