Ca glue.....joint longjevity

[Jay Jolliffe]

I have to build a Shoji door with a design that has end grain & lap joints. I was wondering if ca glue will hold up over time.

[Philip Rodriquez]

If the joinery is done properly, the glue will hold. However, PVA (wood glue) is a better choice. CA glue is too thin for most applications.

[Prashun Patel]

I'm not sure what you mean by end grain and lap joints...
Are they half-lap or bridle type joints? If yes, then the right glue will hold this very well. If one of the mating sides truly is end grain, though, the glue will likely not be strong enough.

You're better off using wood glue for this.

[Cody Colston]

I've heard that CA glue will break down over time. I don't know how factual that is but why use CA glue for your application?

PVA glue is a proven product, it's much cheaper than CA glue, it cleans up with water and any squeezeout/residue can be wiped off or scraped off. CA glue squeezeout will soak into the wood and permanently stain it. The only way to remove that stain is by aggressive sanding.

[Kyle Iwamoto]

According to some of the CA makers, CA is a "lifetime" joint. It should not break down or fail. I personally don't know if it's true or not, but that is what they say. Of course, there are several CA makers, so YMMV. That said, Titebond or those PVAs are a MUCH better glue to use for all the reasons mentioned. Unless you are glueing some thing else to the wood, such as the screen material.

Just my $0.02.

[ian maybury]

Hi Jay, I worked in adhesive applications for some years including with CA, but am not an adhesives chemist. i.e. what i have to say is received knowledge, and subject to my memory being correct. Check it out with the applications/tech support guys at a good maker like Loctite if the application is in any way critical. They will probably play safe though if it gets too detailed.

In answer to your question the answer is probably that it all depends. CA is a bit of a mixed bag as adhesives go - it has properties that make it irreplaceable in some applications, but many shortcomings too.

There's quite a wide variety of types and formulations, and these can vary quite widely in properties. The following relates to the more or less stock types sold for consumer use.

At the most basic level the cured polymer is regarded as long term stable, and is resistant to many chemicals, including water. It's not that simple however in the context of a joint.

First off the polymer is very brittle, so joints subject to cycling loads (e.g. expansion and contraction of wood) or sharp shocks can fail unless the substrate is flexible, and not too stiff.

It won't cure through gaps much above 0.015in (ideally less) without an accelerator (it relies on surface moisture to kick off the cure), but using one delivers reduced properties.

Some solvents dissolve it, and it doesn't have much temperature resistance (there are high temp grades, but it's generally weakening considerably by about 60 deg C, and melting by 120 deg C) The tech data sheet here might be useful: http://www.ellsworth.com/display/productdetail.html?productid=867&Tab=Vendors

It largely bonds by (a) wetting/electrostatic action, and (b) by penetration of the substrate which enables interlocking on cure. Impervious materials like plastics and e.g. non porous woods would depend largely on (a), while on porous materials where the liquid polymer can wick into the body of the material by capillary action (b) is very effective.

The electrostatic bond (a) is unzipped by water and many solvents, so while the polymer itself is waterproof, the bond on impervious materials like plastics and metals is likely to fail in damp or wet conditions. This might also be the case on wood varieties where oils or the physical make up don't quite prevent bonding, but do prevent the adhesive from penetrating deeply into the fibres. Bonds on porous woods are waterproof due to the interlocking.

Another consequence of it's brittleness and inflexibility is that it fails fairly easily in peeling situations. (all adhesives struggle with peeling, and work best in shear anyway)

One final caveat is that a very acid wood may make it hard to get a cure - even with an accelerator.

On the other hand it's very widely used in structural applications in model aircraft on balsa wood where it performs very well - balsa is porous, flexible, non acidic and not too strong.

So what does all that mean? I'd say it's a decent shot on porous, flexible, non oily and non acidic woods in joints that won't get wet, or be shock loaded e.g. dropped - where other properties like e.g. the ability to wick into the gap in a dry assembled joint, or the speed of cure make it a good choice.

Lots of testing is advisable though, and it can be magical stuff when all the factors line up. That said there's many much more robust adhesives. It's expensive and smelly too, and likely to produce a blooming effect on sealed surfaces as the monomer is very volatile. i.e. it vapourises when wet, cures on contact with these surfaces....

ian

[Jay Jolliffe]

What I'm having to do is make a Shoji door with a design in it.Frank Lloyd Wright goes to Japan. All the cuts at the diamond points will be end grain & all the other joints on the design will be half lap. The two diamonds, will have glass in them.....

Sorry about it being side ways but I'm on dial up & if you knew how long this took......I hope you can get an Idea....

[Adam Strong]

CA glue is alright to use so long as the parts are a tight fit. CA comes in many viscosities but none of them are as good as a good wood glue if things don't fit tight. I use CA in building RC airplanes, as do most people in the hobby. I would not say the airframes are subjected to heavy loads, but the control surfaces and hinges are put through a bit of load and all the joints see vibration from the engine. I have never had a properly fit joint fail, and don't expect I ever will as some of the aircraft I own are 25 years old or better. Prolonged high heat (200 deg f) will weaken CA, but not much else will. The main concern I would have with your project is making certain to not get any CA on the surface to be finished. Thin CA wicks through the material very well and would be difficult to sand out thus ruining your finish. Also remember nothing glues to skin faster than CA, CA is used to seal wounds all the time.

[Mark Duksta]

I've used this stuff all around the shop:Instant Bond CA Adhesive (http://www.woodcraft.com/Product/2021102/24493/Instant-Bond-CA-Adhesive-Thick-2-oz.aspx).

This is amazing stuff. I glued a couple of pieces of BB 3/4" plywood together to form an L shape. I brought the glued up pieces to work and challenged my coworkers to break the joint. Nobody could.

I bought it to build some jigs I was working on. The jigs have stood up to some major stresses. So far no problems. I used only the glue, no fasteners.

Mark