Wrinkling of Oil Paint Films

[DSmall]

Hi there,

I'd like to enquire about the permanency of wrinkled pain films. I understand this is considered a technical flaw arising from the proportion of binder to pigment, or a heavy application of paint made up with a polymerised oil, or the heavy application of siccative pigments (ie. cobalt and manganese colours which are surface driers) whereby the surface of the paint film forms a skin stifling the oxidization of the underlying paint and therefore causing the skin to shift with movement of the underlying paint. I figure that once the wrinkled film has dried through, there would be no further technical issues aside from the eventual yellowing of the oil (which would obviously be quite severe due to the amount of oil). Am I correct to assume this, or will there be further adverse changes to paint film within my life time, say the next 70 years. You would be right to assume my intention is to cause the paint film to wrinkle for a certain effect.
I would also like to ask for your thoughts about the addition of large amounts of fumed silica to polymerized oils, ie. epoxide, stand or long oil alkyd mediums and combinations thereof, made up on the slab. To this I have added very small amounts of synthetic lakes, ie. pthalo green, to colour the gel-like silicon/alkyd-oil mixture which I have then thinned slightly with Mineral Spirits and poured onto the surface of lead primed linen canvas (lying horizontally). It is a very beautiful effect, however I do have my reserves about how sound this will be; I do not desire the work last a million years though preferably both mine and the buyer’s life time. I figure the silicon will trap the binder and prevent it from shifting too much as it dries. I just wonder if this is too fine a pigment (if it is considered a pigment at all) to create a strong paint film.
Any thoughts would be welcomed. And, yes, in case there was any confusion, I am an abstract painter. Your advice will be appreciated as always.

Thank you and best wishes,
Daniel

[George O'Hanlon]

Daniel,

There are a number of conditions that can cause wrinkling on paint surface. One condition is when a newly applied layer of paint dries faster than the lower layer. Since oil paint increases in weight and volume as it cures, and then returns to nearly its former weight and volume (not allowing for the evaporation of solvents and other volatiles), the upper layer quickly passes through the induction and curing before the lower layer has a chance to complete this cycle. The slower change in the lower layer causes the upper layer to stretch and then contract causing the wrinkling effect.

Another cause of wrinkling is due to applying a thick layer of paint. This is a similar cause as to the one described above, but in this case, the surface of the paint dries faster than remainder of the layer, cutting oxygen from the lower part of the layer and hence slowly its drying further.

Yet another cause of paint wrinkling is excessive moisture. If there is much humidity, the moisture retards drying of the paint, which may not dry thoroughly. Again, the surface of the paint may dry too fast and it will in turn wrinkle.

There are, of course, other causes of wrinkling, such as applying a paint layer containing aggressive solvents over a layer that is then softened. But the ones described above are the most common in oil painting.

All these forms of wrinkling, in many cases, eventually lead to poor adhesion of the upper layer to the lower layer.

Wrinkle paints, on the other hand, are made using a catalyst to cause the wrinkling that result in hard, stable finishes.


Excessive amounts of silica, fumed or otherwise, can create weak paint films, whereas small amounts can actually increase the strength of a paint film. What is a large amount?

[Brett Barton]

Excessive amounts of silica, fumed or otherwise, can create weak paint films, whereas small amounts can actually increase the strength of a paint film. What is a large amount?

What constitutes an excessive amount of silica? I'm exploring the use of fumed silica as a bodying agent for application of thicker layers of highly transparent color, where "thicker" means amounts spread by a painting knife without scraping (generally less than 1/16 inch, but sometimes approaching 1/8 inch). I'm trying to allow the paint to stay put but also not wrinkle. It may not be possible with thicker application of paint, but I'm trying to see if there is a way for it to work.

edit: I should probably add that I'm mixing the fumed silica into alkali refined linseed oil. I then use the resulting medium with varying amounts of oil paint to make different intensities of clear color.

[George O'Hanlon]

What constitutes an excessive amount of silica? I'm exploring the use of fumed silica as a bodying agent for application of thicker layers of highly transparent color, where "thicker" means amounts spread by a painting knife without scraping (generally less than 1/16 inch, but sometimes approaching 1/8 inch). I'm trying to allow the paint to stay put but also not wrinkle. It may not be possible with thicker application of paint, but I'm trying to see if there is a way for it to work. Edit: I should probably add that I'm mixing the fumed silica into alkali refined linseed oil. I then use the resulting medium with varying amounts of oil paint to make different intensities of clear color.

An excessive amount of silica depends on many factors, so there is no easy answer. However, it would be difficult to add an excessive amount of fumed silica to your paint, because it would quickly become unworkable. Add about 1 to 4 percent on the basis of weight of the paint or formula. As a "bodying" agent I would not recommend fumed silica alone, but rather other types of extender pigments, such as calcium carbonate (calcite), barium sulfate (barite), magnesium silicate (talc), silica and calcium sulfate (gypsum).

[Brett Barton]

George, thanks for your reply.

The reason I was interested in fumed silica is that it affects oil without reducing its transparency. Are any of the other extender pigments you listed optically clear when mulled in linseed oil? I've tried fine silica and ground quartz, both with very similar results: the medium created didn't drastically reduce transparency, but did add a cloudiness. In masstone the mediums were both off-white.

[George O'Hanlon]

The reason I was interested in fumed silica is that it affects oil without reducing its transparency. Are any of the other extender pigments you listed optically clear when mulled in linseed oil? I've tried fine silica and ground quartz, both with very similar results: the medium created didn't drastically reduce transparency, but did add a cloudiness. In masstone the mediums were both off-white.

The extender pigments are essentially transparent in oil, but the particles scatter light and hence give the appearance of color to the oil. However, when you mix this with a pigment, the pigment color is only slightly affected by the extender pigments.