Wetting canvases

FramerDave

PFG, Picture Framing God
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I'll post this here so as not to threadjack the other topic, Canvas Painting Without Stretcher .

Someone suggested wetting/spraying the back of the canvas after stretching to tighten it. Others advised against it, pointing out that it could damage the ground/gesso that was put on the canvas to prepare it to recieve the paint. Hugh pointed out that wetting some canvas could cause it to actually stretch, making it looser.

My question: What is the logic behind wetting the canvas to make it tighten up? I suppose the theory is that it will cause it to tighten up, but what would keep it tight after it dries? Wouldn't it just loosen up when the ambient humidity goes up?

Or one could wet it before stretching, on the theory that it would contract and tighten up as it dries once it's stretched, sort of the way we used to do with dust covers. But assuming it did work, wouldn't it have way too much tension on it, epsecially during a time of very low humidiity?

I guess I'm with Jim. I wouldn't do it.
 
If you don't know if the ground is water soluable or not - don't wet the back. I've seen the paint just flake off canvases that got wet.

That's what the keys are for - to slightly take the sag out of saggy canvases.
 
In my prior life, I was a traditionally trained artist. I often stretched my own canvases, and applied the ground layers. If the canvas was not quite taut enough, we were taught to mist the back of the canvas lightly and to let it dry throughly BEFORE applying the gesso. I have to admit, I've also done it to plenty of my own pre-prepared canvases, but usually prior to painting. (I have also dampened the back of small areas of my paintings to "pull" out small dents... :rolleyes: )

Because I rarely know exactly with what or how a client's canvas was prepared, I will almost never dampen the back of a canvas that isn't mine. Jerry, I think you are probably correct about the newer acrylic-based grounds, but why risk it?
 
I have sprayed them from time to time. Depending on whether I am using bars with keys. Sometimes there isn't enough canvas to get as good a stretch as you want. Sometimes they come in saggy and have no keys.

I recently got a print on canvas that came in stretched and it was more than a tad saggy and I did not want to wait 2 more weeks to get another one. There was no room to try to restretch it so I chose to spray the back. Big mistake. The moisture showed through to the front. Big splotchy water spots. I was completely annoyed with myself so I went home annoyed. When I came in in the morning it had all disappeared, so I was lucky. Disclaimer: I never would have sprayed the back of it unless I knew it would have been at my cost to replace it. I don't randomly go around spraying unknown possibly valuable works of art. I'm only sharing this just in case somebody htinks canvas is canvas. It tightened up nicely too.

I think the water only works if the canvas has cotton in it which is known to shrink.
 
I think the water only works if the canvas has cotton in it which is known to shrink.
That's the other thing. it will shrink, but for how long? What happens when it relaxes again?

There was no room to try to restretch it so I chose to spray the back. Big mistake. The moisture showed through to the front. Big splotchy water spots.
Blooming is another danger. Moisture can wick through the canvas and react with the varnish, causing a whitish area called bloom. Not good.
 
Dave, Thanks for kick starting this post.
I use heavy acrylic on 10oz cotton primed canvas. Never used anything else. Spraying tightens it and keeps it tight for years. Never a problem.

I have yet to stretch another artists canvas or frame a "loose" piece. I thought I could just spray any piece and assumed it'll have the same effect. Apparently not.
I'll keep my eyes on this post and see where it leads.
 
According to Vivian Kistler in Mounting Methods, Volume 5, p. 65:

It is no longer considered appropriate procedure to insert corner keys, although the slots remain in the bars. It has been noted, that overtime the keys disfigure the canvas by pushing out the corners.
I would never wet or spray any medium on canvas. Have you not heard all of your life that "oil and water don't mix". We did however remove a dent in an oil on canvas by appling a hot, damp cloth to the back of the dent. After a few hours and repeating the process, the dent was gone. All done with a signed disclaimer from the customer.
 
I would still surmise that carefully keying out a canvas that has become loose is still less stress than removing the canvas and restretching it...

Dave Makielski
 
Speaking of tighten up there is a canvas retentioning spray out now called, you guessed it, "Tight'N'Up" that you may want to consider for this purpose. You should be able to find it at art supply stores (like ours)Maybe some framers suppliers carry it? It's from Masterpiece of S.F. CA, a good reputable company and comes with all the usual archival & safe claims. I've used it (originaly at the request of an artist) and a couple times since. Once on a oil ground canvas (not yet painted on) where the canvas was terribly distorted and a couple times on those cheapie tourist sort of canvases and I'd say it worked as advertised.
(The)Tighten up is also a great song (and dance) By Archie Bell & the Drells.
 
I bet I spray the back of a canvas maybe 1 out of 10 canvases I stretch. Sometimes it is all that works. I just had some really horrible paintings from \Jamaica(mon), they were painted on flour sacks. I could tell just from inspecting the canvases before stretching that there was no way they were gonna stretch well enough. Spraying that backs tightened up what I could not. As I recall, I had about a half an inch to stretch with too. On these particular canvases they had been stretched and unstretched for shipping. The canvas had already formed iteslf around stretcher bars and refused to stretch any further to flatten out the many puckers. Misting water on the back helped that along and they ended up looking great.

It is not to say every canvas gets sprayed. I've been framing for 20 years and I never even had a canvas stretch fail to my knowledge, with the exception of giclees, they seem to fail for me at an alarming rate. But, I know better than to spray the backs of those. Obviously, you have to be smart about it.
 
If mechanical tensioning is no longer used, why are their mechanisms to tension the canvas on every new stretcher made for replacements that conservators use? Why does the Lebron Company sell tensionable stretchers to museums, galleries, conservators and artists?

I liken the use of adding humidity to a deformed canvas to the use of prunes in treating irregularity. How can you know in advance the quantity needed to get the desired results?

Mechanical tensioning is much more easily controlled, especially with the use of threaded tensioners, than the relatively uncontrolled use of humidity.

We have discussed this topic before, and as before I would really like for one of the preservation experts to speak up on the matter. There is too much ambiguity on the subject, and very little real science being spoken. There are probably no absolutes, but a "rule of thumb" would be nice.
 
Lebron style stretchers are without doubt the tops. Tight'n'up does a good job of taking out dents. Some of our artist customers like tight'n'up because they don't think the canvas will ever loosen back up after useing it. I don't neccesarily endorse that. I don't know what exactly is in it, it's not listed. Find it on Masterpieces' website. http://www.masterpiecearts.com/products/tight.php
 
Originally posted by FramerDave:

My question: What is the logic behind wetting the canvas to make it tighten up? I suppose the theory is that it will cause it to tighten up, but what would keep it tight after it dries? Wouldn't it just loosen up when the ambient humidity goes up?
To answer your question(s). This is an "old school" practice. And yes it will tighten stretched canvas. However, as with most old timer tricks, folks remember only part of the process, and or theory for the practice to actually work.

The therory is the water will indeed shrink the fabric. Why. Ah ha. That's what is not mentioned. It iwll shring the fabric the same way an all cotton shirt will shrink in a hot dryer.

So, you need to spray/mist HOT water, and the backof the canvas needs to be put in the sun (or heat gun, but that's a bad idea if you are not experienced).

Commonly done the artist (or framer who made the canvas for them) after the canvas was made and streched. But befoer painted upon. If it is done after being painted, it depends upon the paint film. But in general, if you know what you are doing, it can be done. If you don't this has bad idea written all over.

And then you ask:

Wouldn't it just loosen up when the ambient humidity goes up?
Did that shrunken t-shirt or wool sweater ever get bigger again. How about that pair of 501's that you used to buy and wear wet till they shrunk, in the bays before pre-shrunk (and pre-distressed) cotton jeans?

No.

Now, the big risk of bad things happenign is not acutally witht he paint film.

The big risk is that you will bow the stretchers (inward), or have it go out of square.

In extreme cases, actually crak the stretcher, or cause a rupture (tear) in the canvas. Usually at the edge, or where it meets the stales or nails.

This is however rather rare, as again, the "old shcool" methods/practices are not completely rememberd.

If you are doing this, and want to get the extra snap on the canvas, you don't just use hot water, and warm sun. You mix Alum with the water. Y'know. the stuff that Tweety feeds to Sylvester so his mouth shrinks so tiny and small he can't fit the Tweety (or the large turkey on the table) fit in his mouth.

Of course, Sylvester then takes the Alum and sprinkles it on the turkey and it shrinks, and he then fits it in his shrunken mouth.

In old art (and framing) supply catalogs they even sold alum.

the amount of alum will effect the amount of shrink. Again, a great recipe for bad things if you don't know what you are doing. But a great tool for those with an understanding and experience with the practice.

Did that help 'splain it out?
 
As Hugh mentioned earlier, the subject is very complicated. Thank heavens I don't have to deal with it, and have happily let the subject lapse in my memory banks.

Some of the variables I DO remember, are weave (this can vary tremendously) and fiber content. Linen behaves very differently than cotton when wet and dried. This is how weavers can get some 3D into their woven fabrics - warps threaded in cotton/linen stripes, and then washed after it comes off of the loom. It gives some nice puckering texture because of differeing textures.

So if the canvas has mixed fibers, or is slightly warp or weft faced, or has a 2-2 weave, you'll get different results when misted.

Add the complex mix of size, ground, paint and varnish layers, all of which can have a wide variety of compositions, some stable and some not so, (even commercial mixtures can have "Friday lemons", like cars) and you have a lot of variables in the mix.

These are some of the reasons why sometimes the mist will work, and sometimes it won't. Sometimes it doesn't cause damage, sometimes it does. A paintings conservator could tell you a whole lot more - perhaps it would be a good subject for one of the tradeshow workshops or lectures.

Rebecca
 
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