Stripy bowl glue

[Leharrold]

I've been asked to make some bowls with laminated acrylic and oak so they use wood from a particular tree and are stripy, what do people think I should use to glue them up? I was thinking maybe cascamite but this is a bit of a stab in the dark really! Any thoughts welcome.

Cheers,

Laura.

 

[tekno.mage]

Not sure Cascamite would really be suitable - it may go an odd colour. I tried it once mixed with oak sawdust to fill a crack in an oak bowl and it went a nasty khaki colour once set. :-(

I'd use a decent quality PVA type glue, like one of the Tightbond glues - we use Tightbond II to laminate pieces of various woods before making shawl pins and it works fine for this.

 

[Leharrold]

Yeh it was the colour I was worried about! Ok Tightbond sounds like a plan, will do a test! Thanks for your help.

 

[mikec]

Hi Laura,

We had a demo by one of the exponents of laminated acrylic and ply forms, age prevents me from giving his name #-o

Because the acrylic and wood have different thermal expansion coefficients there is a danger of fracture especially when turning if the adhesive is too rigid.

His recommendation is a specially formulated CA glue with rubber additives.

I use "Clear 'n' Tuff" from Starloc 5Star adhesives, it is slow enough to give time to position and is flexible enough to withstand thermal and mechanical shock better than standard adhesives.

I use them for all my CA glues, they are very reliable with a long shelf life, especially if kept in the fridge.

Regards,

mikec

 

[CHJ]

A few observations,
I would make sure your acrylic mating faces are abraded to form a key if using a wood glue.
PVA will creep a small amount as the wood and acrylic move at different rates of expansion/moisture level, not much but enough to feel the joint after a while on something like a bowl.
Cascamite sets hard and does not creep, but I would not expect it to hold well against the noporous acrylic, I suspect any non deliberate colouring on Oak is down to iron contamination between the mixing water and/or tools used and the oak tannins.
As the acrylic is non porous I would sertainly give CA glue a trial.

What ever you do make sure that the Oak is as dry as you can possibly get it (below 8%) and that you rough cut it into suitable stock and give it time to release any stresses before you finish to size prior to cutting segments, Oak is a strong wood and will do its own thing, 1/2deg. change in all segment angles after it's glued up can break the bonds, especially as you are bonding it to a rigid substance.

 

[woodyturner]

I used CA glue on a wood finial with acrylic inserts and it is still stable after about 11 years also I made quite a few lace bobbins with acrylic inserts that are still in use I have also set acrylic into wooden boxes some years ago and they are still as stable as the day I made them one thing I did was firstly soak the area in thin CA first then after it had dried I used a thick ca to fix the acrylic in place Hope this helps

 

[Leharrold]

Hmm yes that's true about the movement..I'll try CA glue on a little tester egg cup first! The Oak is now very dry so hopefully should be ok, will try and let you know how I get on! Thanks for all the help, much appreciated.

 

[CHJ]

Hmm yes that's true about the movement..I'll try CA glue on a little tester egg cup first! The Oak is now very dry so hopefully should be ok, will try and let you know how I get on! Thanks for all the help, much appreciated.

Making something like a bowl with segments of differing materials is significantly more difficult to achieve than using alternate materials as inlays or embellishments, the basic structure is relying on the dissimilar materials bond and there is no underlying support structure.
So take great care in how you clamp and support the bowl blank for turning and avoid a catch at all costs.

 

[dickm]

Somewhere else on the forum there was a discussion of adhesives for acrylic plastics - cascamite would almost certainly not adhere to such a smooth surface (certainly not to the interior of yoghurt pots when used for mixing!). The standard way of sticking acrylics is some form of solvent, isn't it? The sort of stuff used for sticking plumbing or electrical fittings would probably work, because it would dissolve into the surface of the plastic, but has enough filler in it to attach to the rougher surface of the wood?
Possibly!