As I reach the end of my titanium white supply, I am revisiting the decision to again mix a 50-50 lead-titanium white for painting.
Titanium white gives a greater opacity over time, but my understanding is that it creates a “softer” paint film.
Lead carbonate white has less opacity, but creates a stronger, harder paint film.
I mix them to hedge my bets with some of the good properties of both.
As I now paint almost exclusively on 10 mm, honey combed, aluminum panels, which will not bend , expand, or stretch like stretched linen, how important is it to have a “strong” paint film?
As I am now using a 25-75 walnut alkyd-OMS medium, is there enough strength and flexibility provided by the alkyd to eliminate the lead carbonate?
I tryi to keep things simple and the paintings “permanent” and when there is an opportunity to do so, I question my methods and materials.
Thanks for your help,
Richard
PS Not sure that I can do anything more to provide permanence in my paintings. Painting on panels is a biggie.
Thannk you, George.
So, 20% titanium dioxide and 80% lead carbonate would be the optimum for both strength and opacity?
Would you recommend lead oxide alone?
Whoops. The last question should read, “Would you recommend lead carbonate alone?”
White lead pigment not only catalyses the drying of oil paint it also builds a network of lead soap structures and hence reinforces the dried paint [ J. J. Boon, F. Hoogland, K. Keune, “Chemical processes in aged oil paints affecting soap migration and aggregation,” AIC Paintings Specialty Group Postprints, 2006, 19, 18 – 25]. Lead white is not such a strong white pigment as titanium dioxide, but it does have slightly pink cast which may be useful. Titanium dioxide pigment does not have any effect on the drying of the oil, nor does it form soaps, so it does not help the eventual properties of the dried film, in that sense.
Stuart Croll
I have sent this question to one of out modereators who is up to date on this subject.
A typical ratio of titanium dioxide pigment and extender pigment in commercial oil paint is 20% and 80%, respectively. You can use this ratio as a guideline for mixing basic lead carbonate (lead white) and titanium dioxide (titanium white) pigments for your white.
Although a rigid panel may place less stress on an oil paint film, lead white also makes an oil paint film less sensitive to water, which titanium dioxide does not do. So, even if you are painitng on a rigid panel, it is still recommended to use lead white in your oil painting.
You can start with the 80:20 ratio, which we have found to be optimum, but you can increase opacity of the mixture by increasing the amount of titanium dioxide. We have found diminshing returns when significantly increasing the amount of tritanium dixoide.
Lead white by itself usually provides sufficient opacity for most applications, but for brighter highlights you may we try the mixture of the two whites.
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