stretching canvas on board

[nickhood]

Hi, I have a rather thin canvas from China to stretch. There is very little plain canvas around the image and customer doesn't want to loose any of the image so stretcher bars are out. Furthermore the stretched image will not be framed. I have suggested stretching it over a board and building a sub frame to keep it flat. The image is 1200 x 500mm. What thickness of MDF would you suggest for some thing this size. Any help would be welcome.

[prospero]

If you can't use bars then how will a board help? Unless you mean stick it to a board... That's probably the only option given the customer's wants.

I would do it on 2.5 MDF. It will be a bit bendy but that is where your subframe comes in. Use square timber with a 2-3 cross braces. and glue the mounted canvas to that. Then you have to tidy the edge. This is the awkward part. The chances of sticking the thing down with a perfect edge are slim so you may need to trim a nidge off the image. Then you have to have the MDF and the edge of the subframe dead flush, so you may need a bit of trimming there. Once it's done you need to paint the edge. Without getting paint on the face. Black is probably fav. Altogether a not inconsiderable faff, so charge for it.

Much easier to drop a minimal frame around, which would actually be cheaper. So if the customer wants it this way purely from (what they perceive) an economic perspective, but sure to enlighten them.

btw. There is no advantage to using thicker MDF. If a 2.5 board curves a bit when the mounting glue dries then it is weak enough to be flattened by the subframe(as long as the subframe is flat). If thicker MDF bends it's likely to remain that way. In any case, give the back of the board a coat of thinned glue or varnish to seal it.

Remember. Despite what the customer may imagine, this is not a cheap framing option.

btw. To stick it down I would use PVA. You will need two hefty boards to sandwich it between and some release paper and a foam blanket big enough to cover the whole lot. And a lot of heavy stuff to pile on top and leave overnight.

[IFGL]

Prospero, could you clarify in nats bollocks the size of a nidge?

[prospero]

It's almost a spider's eyebrow shorter than a tad.

[nickhood]

Thanks Prospero, I agree a small moulding would be the obvious solution to neaten up the edge and help keep the board flat. I think I will ask customer to come back and discuss the options. Thanks again