stretching a canvas

[whitehorse]

Hi, I have been asked to stretch 4 images on canvas well more like cotton really, onto a frame. The largest is 60" x 39" and as I have not stretched anything this big before I was wondering if the stretcher bars from Lion would be suitable. Any advice would be most gratefully received. Thanks.

[MITREMAN]

Hi Whitehorse,
I would use a Premium bars
39 (991mm) x 60” (1524) with cross braces.

An alternative is to make a mitred strainer from 1” x 2” timber, Bevel off edges or use a stretcher profile timber.

You can notch in a centre bar with the Morso (arrow points at both ends of the brace set into a mitred notch) to hold in position tap in by hand 10mm wedges.

You would need to dampen the canvas before stretching.

As the corners are fixed you will not be able to re-tension without spraying or removing tacks/staples and re-pulling,

Premium Bars

Assemble the bars making sure they are square, measure the diagonals from the outer corner they should be the same length to be square.

Mark on the edge of your canvas with chalk the centre of the length top and bottom and the same for the sides.

Now find the centres on your stretcher bars and mark.

Lay your canvas over the bars matching the centre marks, tack in the middle at the top of the longest stretch (tack on side edge) and tack at the bottom. Repeat for the sides.

You know have 4 tack/staples points pull out the canvas as best as possible and do a four temporary tacks on the long side at each corner.
(They are there only to help you keep the artwork in the correct location)

Now spray mist the back with distilled water.

Now stretch as normal working from top to bottom along the long lengths a few tacks at a time and rotate tack a few more and rotate back, you will need to pull hard by hand or with stretching pliers across the width and taking up the slack along the length.

As you get nearer the temporary tacking points at the end of the long bars remove them and start stretching the width.

The corner points should be folded in point first then each flap and tacked.
(Do not staple across the mitre joint)

Put in the wedges making sure the ends of wedges slope inwardly towards the mitre,
if they are at 90 degees they will not lock

Protect the back of the canvas with card while tapping the wedges in to take up the strain.

Neaten all loose canvas with tacks.

Job done.

MITREMAN

[markw]

You would need to dampen the canvas before stretching.

Be very careful wetting canvas - If you can check a small area to make sure that the image wont be affected. keep any dampening to a minimum.
You have to bear in mind that some images that come in on fabric that was never meant to be stretched, wont stretch. stretching them will put the material under forces that it just can accommodate.

If you have that situation then proper stretcher bars are the best choice - you can fasten the material without putting a lot of force into pulling the edges - then very carefully tap in the wedges to get a reasonable tension. Over tension and the material could rip.

[MITREMAN]

MarkW,
Agreed, good points mark forgot to mention them.

MITREMAN

[whitehorse]

Hi, just wanted to say thanks for the advice, most helpful.

[prospero]

May I just butt in to say the the term 'stretching' when applied to paintings on canvas is a little misleading. The canvas should be just held taught, so it does not flap about. No need to get it 'drum tight'.
The only time you need to exert extra tension is if you want to pull out a bump or a wave and this should be done slowly, accompanied by gentle moistening.

[markw]

Canvases in their natural state - primed and naked are fairly tight - the priming providing that little bit of take up in the canvas. The restretching of a canvas could almost be seen as a process that really shouldn't be tackled as you are trying to achieve a result that is post production and the chance of damaging the paint on the canvas is relatively high. So, I agree that attempting to get a painting thats been painted without stretchers drum tight is actually damaging to the work.

[Bill Henry]

When I read your post, I keyed on the phrase, “more like cotton really”.

When I think of cotton (in the framing environment), I think of an unsized, T-shirt like material.

If so, it makes me think that the material will not suffer stretching well. Not only may it distort easily, but without sizing, the fabric may tear when you put tension on it especially with one so large as yours.

If not, … well … never mind.

[MITREMAN]

All Good points,

WhiteHouse I wonder if you could post (photo) a corner section of the Material so we can see the edge to define its makeup and the image.

Then we can offer you better advise.

Some large images do require a lot of pulling to get square, I have done many large paintings some being over 3inches out of square from corner to corner.

As said before do not over tension, Do not over damp, You can crack the paint, tear the canvas, or image as many are on paper mounted onto canvas or printed onto canvas.

As you do more you will learn, sometimes you have to say I can't risk tightning it any more or thats as square as I can get It.

MITREMAN.

[Moglet]

May I just butt in to say the the term 'stretching' when applied to paintings on canvas is a little misleading. The canvas should be just held taught, so it does not flap about. No need to get it 'drum tight'.

That's a really interesting point. 'Drum-tight' is pretty clear to undertstand, but could you give any analogies for how a canvas should behave when it is 'taut' or when it is considered to be 'flapping about.'?

Also, for those with greater longevity in the trade, just how much post-stretching relaxation should be expected from:

1. Decent artist-quality canvasses?

2. Nasssty 'orrible nylon canvasses (HK oil standard fodder)?

[MITREMAN]

Hi Moglet,
Follow the link below and you will find many Clips on this You Tube page about canvas stretching.
also look at the ones at the bottom left.

As a general rule of thumb if it sound like a drum its to tight, you want about 1/4" slack each way (1/2" overall)

Some are quite good.

[youtube]Lh9T4Sfzgig[/youtube]

MITREMAN

[prospero]

That's a really interesting point. 'Drum-tight' is pretty clear to undertstand, but could you give any analogies for how a canvas should behave when it is 'taut' or when it is considered to be 'flapping about.'?

Also, for those with greater longevity in the trade, just how much post-stretching relaxation should be expected from:

1. Decent artist-quality canvasses?

2. Nasssty 'orrible nylon canvasses (HK oil standard fodder)?

If you stand the canvas upright and move the top to-and-fro. The canvas should not displace noticably in the middle. If it does, it is officially flapping about.

1. A lot depends on the size. I like to leave the newly mounted canvas for a few days for it the settle down. Most will not need the wedges tapping in. Bigger ones might need a slight tweak.


2.I have always found the usual HK oil canvas to be stable and very well behaved. The paintings may be a tad bilious and the actual paint may fall off, but the canvas is not bad stuff on the whole. I've known what appears to be good quality canvas behave appallingly. I suppose they are like fine wines. Some don't travel well.

Just for the record: I never use canvas pliers. I have only had one canvas where I felt I might have needed them. It was very heavyweight canvas, thickly painted. Had the consistency of leather. Had to knock the wedges in quite a bit to get that one flat.

[Moglet]

Thanks, Prospero!

[markw]

Just for the record: I never use canvas pliers. I have only had one canvas where I felt I might have needed them. It was very heavyweight canvas, thickly painted. Had the consistency of leather. Had to knock the wedges in quite a bit to get that one flat.

The sort of vice like grip that makes people avoid shaking hands with you a second time.....