Hello,
I commonly paint on a good quality, heavy cotton duck (on stretchers) which I paint on unprimed. I size the canvas with three coatings of fairly dilute rabbit skin glue (1:20 ratio) and paint straight on top. I have been doing this for several years, and my usual test of whether the size is sufficient to protect the cotton from the linseed oil in the paint is to check for strikethrough on the back of the canvas – usually my sizing method prevents any strikethrough, and seems successful. I’m also careful not to create a thick ‘layer’ of rabbit skin glue, as I’m aware that this can cause problems of delamination and animal glues in general are a bit vulnerable to the environment. I look for a very slight glittering on the surface of the cotton to judge that the size is going to be effective.
For my most recent project I decided to switch to linen. I have what I think is a good quality linen, but when I’ve stretched and sized it according to my normal method, I’m getting some quite bad results. There is a lot of oil strikethrough happening. I believe that the oil is actually going through the holes in the linen’s weave, and then soaking into the back side, since the weave seems rather loose compared to the cotton I usually use, and I can see pinprick holes. My plan to remedy this issue (on the canvasses I haven’t already started painting) is to add another layer of rabbit skin glue, at twice the usual strength, and attempt to have the glue size ‘plug’ the holes in the weave and therefore prevent paint getting through (so basically the usual job of a primer). Adding a layer of primer isn’t an option because I already have a detailed sketch on the canvas and need my ground to be transparent so I can see it.
Is this an acceptable strategy to mitigate this problem? Is there anything I can do to my initial layers of oil paint to minimise strikethrough? Adding solvent seems to make it worse, as the resulting thinner paint finds its way through the weave even more readily. I have also been considering relaxing the tension by moving the staples, while the linen is wet with glue, in the hope that when it dries and re-tensions the weave won’t be quite so ‘stretched’.
I’ve been reading a bit about the debate over how disastrous strikethrough really is, and it seems a little ambiguous. I’m not sure if accepting the strikethrough is a better bet than experimenting with a thicker size layer? Of course I’m aware that I might end up with oil sinking later on and have to deal with that, but my main concern now is ensuring a stable foundation.
Hi Brian,
Thank you so much for your quick and thorough response!
I should have clarified that I measure the glue by volume (50ml granules to 1 litre water) so I’m not sure how that translates to weight. The granules I use are very fine, like brown sugar, so I imagine the weight to volume ratio is quite high. When I make gesso I usually make the glue at 1:10 by volume instead, but I’ve found that for sizing that seemed too strong, so have opted for 3 x 1:20 layers (I’m not sure if layers present any issues in themselves!)
I decided to go for it on the linen and apply another layer of stronger size. I let the glue cool quite a bit before applying, so that it wouldn’t soak in so much, which worked quite well. A preliminary bit of painting seems to be behaving more normally and I don’t see any strikethrough which is a relief.
As you mentioned, this really tested the stretchers! I have experienced slight warping of the bars, but the plane of the linen is flat. I plan to re-stretch the paintings later anyway after transporting them, on new stretchers if necessary, so I hope I can fix that later.
All in all, the experience has been a lesson in the risks of swapping around materials and methods without doing a test first (and when in the countryside with limited materials available)! I think in the future I will stick with the robust cotton duck since it works very well for my purposes, and it seems I would need to spend even more money on linen to get an equivalent quality of weave.
Thank you so much for your help!
Laura
There are many aspects to your post. First, it brings up the subject of whether animal glue is an appropriate size for fabric. It does have its issues beyond its reactivity, and the fact that it is a poor gap filler as compared to acrylic dispersions and PVA dispersions). Let’s forget about that for the moment. In truth, as an oil painter, I always sized my cotton and linen fabric supports with animal glue.
Your proportion of glue to water does seem very slight. 1:10 or 1:15 is more commonly recommended in terms of weight in grams to ml in volume. I have also had problems with using too dilute glue for sizing.
While it is true that the glue will somewhat fill the open interstices of the fabric, much of what it does is shrink and stiffen the fabric reducing the spaces in the interstices. It is likely that your cotton duck was just more tightly woven than the linen you are using.
I would try gently sanding the canvas and then apply a more substantial layer of glue. I do not think that stretching you canvas more loosely will accomplish much. You do have to make sure that your stretcher system can take the tension.
As to the danger of strike through, this depends on a number of factors, but it is true that EVENTUALLY the fatty acids in the linseed oil will likely cause some cellulose degradation (do a search here, I know that we covered this in greater detail in the past) but some of it has been exaggerated. It is still something to avoid.
As you would expect, one of the ways to avoid strike-through is to make sure that your paint is not overly diluted. This is as true with the application of an oil ground on sized fabric as it is with applying oil paint proper on canvas with only a size and not a ground.
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