cellulose issue - need help

[Not your average framer]

Having though about this one, my instinct is to suggest that you change to another wood glue. One of the main differences which exists at the corners is the presence of a material not present elsewhere, namely the glue.

I don't know enough about the glue in question to be sure about this, but quite a lot of modern glues are formulated to have just a little flexibility to help the joint resist the effects of strain and shock. My hunch is that if you change to using Cascamite, which sets absolutely rock hard and has no give whatsoever, it will solve the problem. If the primer was suspect, I would expect more consistency in your problems, such as substantially more failures. If it's water from the primer causing the wood to swell, I would also expect substantially more failures.

If the issue is caused by movement at the joint, then the glue would be my first concern. Elliminate the glue by substitution with cascamite and see what happens. If you need to, you can move on to elliminating the other possibilities later.

[raph.basan]

Yay Monday !!!

Prospero..... when using biscuits do you place them quite close to the face of the frame or a few cm under the face ? i tried placing them about 1cm under the face of the frame, this did not work as we still had a few mitres opening.... i then placed them closer to the face, this seems to have stopped the mitres opening, but we now have this paint issue ? could it be the biscuit swelling that causes this ?

Raph

[prospero]

I usually place them in the middle of the thinest part of the moulding, toward the inside. This leaves the back to underpin though. I try to avoid underpinning though biscuits.
But I think you should try Mark's (NYAF) suggestions about the glue. The more I think about it the more, the more I think it is the likely cause of your probs.

btw. What sort of shape/size moulding are you using?

[raph.basan]

i'm tracking down a container of the cascamite as we speak... boss says we had some... the offending moulding is tulip, 47mm high, 21mm face, box frame. I've tried a new glue as well today, same frame, different glue, its a polyurethane glue... we'll see in a day or two, i'll have it treated as normal... although this won't be conclusive as we spray a lot and not every frame "cracks" sigh. oh well. got to find that cascamite !!!

raph

[gesso]

Even the best sprayer will find it difficult to control the amount of material going onto the surface and with the physicality's of spaying overlapping areas such as corners it is very common for these areas to receive double the amount of spray. This I still feel is the reason why your having cracking appear at the corners.
I must confess I never spray with cell ,so I'm not familiar with its characteristics, have you gone back to your supplier to ask which would be the best final coating apart from the one you are using?