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How to mix glue
Thursday, 10th March 2011 18:54 PM
When laying complex jointed veneers or burrs it is important to use an adhesive that has no creep. Creep is the elastic quality of some glues after they have set which allows slight movement of the veneer so that joints can open after sometimes long periods. PVA glues are subject to creep. Although D3 rated PVA's are available which are said to be "creep resistant" I would rather be sur eand use a Urea formaldehyde glue such as Cascamite (usually sold under another brand with the suffix "mite"). Cascamite sets to a glass like hardness, so no creep.Cascamite also has the advantage that it does not show up so much when finishing. When PVA bleeds though a burr, as it often will as burrs are usually full of holes, it will show as a lighter blemish when the finish is applied.
Now, the problem with Cascamite is you have to mix it! Mixing a fine powder into water usually ends in lumps and Cascamite is no exception. However I think I have cracked the problem, here is my method for mixing Cascamite:
· Weigh out the powder and water 2:1.
· Add the powder to half the water, stirring all the time. Keep stirring vigorously until you have a smooth paste.
· Gradually introduce the rest of the water stirring all the time.
You should now have a lump free glue mix of a double cream consistency. I like to use 500g yogurt pots as containers for the weighing (I eat vast quantities of natural yogurt at home!). But for the mixing I find a shallower container such as a 500g margarine tub is better as this prevents powder accumulating at the bottom of the container and forming lumps. It's important to get the lumps out at the paste stage as they will not dissolve later.
Another tip when mixing glue when laying darker veneers is to substitute some of the water for a small amount of Vandyke solution. This means that any glue that bleeds through will match the veneer colour. Vandyke is a powder formed from roasted walnut shells. Mix it with hot water to make an excellent stain.
Supplier: www.rydenor.co.uk stock both van dyke crystals and Cascamite (I understand this is the original as made by Borden Chemicals)
Comments…Add yours
Posted by Jeremy Broun on 13/03/11
Hello Chris
You might be interested in my You Tube video on using Cascamite:
http://www.youtube.com/watch?v=0N7LEv2gvLw
Regards
Jeremy
Posted by Chris on 14/03/11
Thanks for that Jeremy. I didn't get to Cheltenham last year, so I didn't see the chair. Hoping to do it this year.
I gave up on Extramite a few years ago. I'm sure the formulation had been changed. It smelt much more of urea and, more importantly, the open time seemed to be a lot shorter, making it a bit difficult with complex glue ups or veneering. I was pleased when I found Rydenor doing the original stuff a few years ago. I always add the powder to the water and make sure I get the lumps out at the half mix stage. I also work on proportions by wieght rather than volume, as volume can vary depending whether the powder is compacted.
Chris
Posted by Martin on 24/04/11
I thought Vandyke is a crystalline powder formed from roasted walnut HUSKS (not shells)? Anyone know exactly how it's made.
Posted by chris on 24/04/11
Hi Martin
You are quite right, Van Dyke is made from boiling up and roasting the husks of walnuts, not the shells (I've checked on Google!). When growing on the tree the nut has a fleshy husk enclosing it. I did not recognise the significance of the difference between shell and husk.
As an occasional restorer I cannot over praise van dyke as a stain, it's richness and ease of dilution make it a very for blending new wood used in repairs or blending down a table top befoe refinishing. I usually add a little ammonia to the mix to give the stain a little more bit and penetration.
Chris