Stretcher bars

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Ed209
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Stretcher bars

Post by Ed209 »

Not had much experience with stretching canvases probably done approximately 20 odd using "Mainline System" and ready sized from "Lion"
Just had an enquiry to do thirty approximately 900x600 and have looked at R&H STR1 these are just joined as per a normal frame so no provision for wedges so just looking for opinions on this method and is the STR1 suitable for the size?
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prospero
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Re: Stretcher bars

Post by prospero »

There are a few 'cut your own size' systems and they do work up to a point. But you can't beat the time-honoured
double mortise and tenon system. The snag is, they come in standard sizes and if you need an odd size (metric?) then
you might struggle find them 'off the shelf'. You can get them made to size from firms such as Harris-Moore, but they
are much dearer than standard sizes.

You can just make a rigid frame and this is perfectly good - that is until the canvas goes floppy and needs re-tensioning.
With the double mortise type you can do this easily by tapping the wedges in a bit and you have 8 points of adjustment
so great control. With a rigid frame the only option is to dis-mount the whole canvas and start again.

The various systems that involve a slot and a plywood triangle are a mixed bunch. I find the smaller one (Wessex) works
quite well if you get just the right thickness ply. On smaller size canvases anyway. The larger 2-way type I find a PITA.

The size 900x600 you mention is close to 36" x 24" (920 x 610mm) If may be the case that it would actually fit with a bit
of difference-splitting and jiggling. Another alternative is to shorten them, but this is more difficult than you might think.
OK if you have a day to spare. :?
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Re: Stretcher bars

Post by Steve N »

On the 900 length, you are going to need a cross brace to stop it bending when you have tensioned the canvas
As tp which type of stretches to use, I think it's down to the canvas, is it the traditional natural canvas, with oil/ acrylic paints or printed canvas, which seem to be made from 'man made' fibres, which I find (IMHO) do not seem to move much or if at all, so do not need re tensioning after a time
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Re: Stretcher bars

Post by Not your average framer »

We've probably all used the cheapest option of stretcher bar mouldings which we mitre to length and then join by convensional means. It's mostly the obvious solution when customers have brought back a cheap oil painting, from a recent holiday and all they want is a cheap job. Unfortunately, it's a bit debatable whether this really is the easiest and therefore most sensible way of doing cheap oil paintings.

Above a certain size gluing oil paintings down onto a board gets somewhat impractical, as the board needs to be thick enough for large painting not to cause the board to bow as the glue sets and the increased weight of the thicker board becomes just too much. Often it is necessary to consider reinforcing the board with a sub frame and even cross bracing across the inside of the cross frame to prevent the board from bowing in the middle.

Obviously more valuable oil paintings should be stretched onto conventional stretcher bars, with wedges to expand the corners and where necessary cross strainers and addition wedges for adjusting the strainers. I would also mention in case some newbies don't realise this, that the strainers and associated wedges are often needed to avoid the pull of stretching the canvas from bowing longer stretchers inwards enough to show gaps between the edges of the canvas and the surrounding frame.

This generally means that framers will not usually have a "one size fits all" solution to suit every need and you will find that different framers will have their own preferred ways of handling this.

O.K., this is my take on this and others will have their own no less valid ways of doing this, I am quite happy for canvases up to dimensions of 20 inches in any direction to use cheap stretcher bar moulding with no provision for corner wedges, when stretching cheap holiday oils on canvas and assuming that these canvases are using conventional cotton canvas, they can be re-tightened at a later date by carefully dampening the rear of the canvas and letting it shrink as it dries.

On larger cheap oils on canvas, I feel a lot safer using stretcher bars made to be fitted with wedges, so that they can be manually re-tensioned. I would point out that I don't like the idea of using normal 20mm deep stretcher bars on larger paintings where the more flimsy bars cannot be relied up on to keep the stretched painting flat as the tension in applied. More valuable paintings are always best framed with better quality and where appropriate also deeper stretcher bar mouldings with conventional wedges to allow re-stretching at a later date as becomes necessary.

I don't stock ready made stretcher bars in various sizes as I have found this impractical and although I am not necessarily recommending this, I will when sometimes avoid placing an order with a supplier just for one job, stick down smaller low value oils on canvas on to 6mm MDF. Obviously, this is always with the customers consent. Be careful, whatever you may be doing when dealing with giclee prints on canvas, as you never know how durable, or adequate some of these may be as suitable for any processes that you wish to use.
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