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Pinguino
01-15-2019, 09:57 PM
Here are my results from "transparent white" test, which I began by asking a question on another thread.

THEORY: No paint is perfectly transparent. But some are very close to it, and that's what I will mean by transparent here.

When glazed atop anything, a transparent paint will necessarily darken the result. If any part of it looks lighter, it is either due to lack of perfect transparency, or the psychological effect of some colors appearing lighter than others, especially in high chroma.

Suppose the transparent glaze is green. If glazed atop the same color green, you won't notice color change. If glazed atop white, it will look green. Atop black, it will not be noticed. Atop some other color, then the result will be a combined effect of the underlying color and the glaze.

If the underlying layer is alternating green and white stripes, then ideally the green glaze will make the stripes disappear. In other words, detail is lost in glazing. Green glaze over other colors will not lose detail.

Therefore, there is no such thing as a transparent white glaze. Since some of every color is present in the white, some detail in every color will be lost when glazed with white. When we say that a white glaze is "transparent" we mean that its opacity is so low that very little detail is lost.

PRACTICE: Now consider the green color Terre Verte (Green Earth), which is inherently transparent. An alternative would be Viridian. The green is relatively dark. So, when glazed over other colors, the result is darker than before, as is usual with glaze.

What if I want to apply a green glaze, but have the result to be lighter than it was before? Merely thinning the green will make the result less dark, rather than more light. If I actually want to lighten the area, then I have to add some white to the glaze, thereby obscuring some detail and creating a slightly cloudy appearance.

Some whites, particularly those containing Titanium Dioxide PW6, are very opaque. To make these have low opacity, it is necessary to thin the paint by adding a lot of medium. A lot! The usual combination of Titanium/Zinc White, PW6/PW4, is almost as opaque.

At the other extreme, not counting merely transparent fillers, is Zinc Oxide PW4. This has inherently low opacity, but some folks don't like the idea of a glaze layer containing much Zinc Oxide. That's an entirely different issue, discussed in many places elsewhere.

But there are other choices. Instead of diluting Titanium/Zinc White with a liquid medium, it is possible to dilute it with a gel medium, so that the result has the handling properties of paint. Although too much gel is not advised impasto, AFAIK it's just fine in glaze. Or, there are other pigments, such as Strontium Titanate (no pigment number, used in Holbein Ceramic White) or Lithopone (PW5, used in Williamsburg Porcelain White). And, it is possible to buy "pre-dilited" Titanium/Zinc White, as with Rembrandt's Transparent White. All of these come in safflower oil.

The below image shows the results. Fromn left to right: Williamsburg Porcelain White, Holbein Ceramic White, Rembrandt Transparent White, Gamblin Zinc White, Gamblin Titanium/Zinc White diluted (by me) with 50% solvent-free gel, and for comparison, Winsor Newton Terre Verte green.

Directly above the labels, on black background, is the white itself. Above them are strips of paint that were slightly tinted (to the same masstone) with green.

The Rembrandt Transparent White was noticeably off-white from the tube, probably because this paint consists mostly of oil and filler. Unilely to be noticed if used in a colored glaze. It is also the most transparent, even more transparent than Zinc White.

Even when diluted with equal amount of gel, the Titanium/Zinc White was the most opaque of these.

The Porcelain White and Ceramic White come in the middle, being more opaque than transparent. To my eye, the Porcelain White is a little more transparent than the Ceramic White. I expect that these two paints might be particularly useful as "mixing white" for direct painting, rather than as "glazing white".

In terms of current on-line sale prices at Blick, from low price to high price: Titanium/Zinc, Zinc, Transparent, (price jump) Ceramic, Porcelain.




http://www.wetcanvas.com/Community/images/15-Jan-2019/1978416-whitesmod.jpg

Dcam
01-15-2019, 10:10 PM
Great test......now what have you gathered moving forward to the easel?
This is a great problem to tinker with.
Yes, that ceramic is a keeper for mixing. I use it as a glaze to lighten areas at times.you can kind of drybrush scumble it on as well. Great for fog, smoke, and the like.
Rembrandt looks like the winner. I'll give it a try.

Raffless
01-16-2019, 04:18 AM
In the test you mention adding white to make a colour lighter. I would add that this applies to areas in the light only. Adding any white to dark or shadow areas is a disaster.

I would also add that before you add white to lighten a colour you should reach for a warm yellow. Because white is cool you are affecting the colour temperature. This can destroy a paintings effect too.

Transparent White is used to great effect when using the Velatura technique. Especially in the halftones. Using a semi opaque white can deliver wonderous effects. Or similarly opaque in the light tones. So your test can help choose the right one.

Harold Roth
01-16-2019, 06:39 AM
The Porcelain white is actually a bit cheaper, I think, if you compare it by cost per ml. To me, the Ceramic looks a titch yellower than the Porcelain, both in my experience and on your chart. Thanks for doing this chart! I'm going to try the gel thing.

Pinguino
01-16-2019, 11:40 AM
I would also add that before you add white to lighten a colour you should reach for a warm yellow. Because white is cool you are affecting the colour temperature. This can destroy a paintings effect too.

Actually, my original purpose was to glaze with yellow, but a lighter yellow than what I have. I wouldn't glaze with whie, possibly except for a fog effect. That's why this is all about using white as a "lightener" for other colors.

AnnieA
01-16-2019, 02:30 PM
That's interesting about the transparency of the Rembrandt paint. Since it's composed of Titanium White and Zinc White, I guess the transparency must be the result of some sort of filler or other additive.