A common filler/extender in oils. Also reference the entry for PW21, which is the artificial variety. In paintmaking, its use differs in water-based media vs. oil-based media. This section focuses on oil, but it is interesting to note that it has a different character in water and is used as in gouache. It is transparent in oil paints.
Barium Sulfate is frequently used as a filler in oil paints, and unfortunately in titanium white it may speed up the degradation of the oil binder according to this article shared by George O’Hanlon.
In contrast to other potential additives such as Alumina hydrate, Barite is heavy and may be added to various colors by paintmakers. Seymour notes in The Artist’s Handbook that this weight can lead one to feel a paint has more substance or higher pigment load when in fact it is the filler that lends weight. Seymour includes an interesting discussion of its complex role in opacity.
Its role in yellowing was first brought to our attention by Natural Pigments, and it may also interact with lightfastness of oil paints, however those results are still preliminary.
Pigments by this name may be natural or artificially made Barium Sulfate. As a filler or extender, its presence is often undisclosed, that reduces the tinting strength of a color.
In terms of health and safety, according to artiscreation, it is possible that this could have soluble barium if it is not made with high standards, in which case that could be quite toxic. Monona Rossol's research also states that PW22 and PW23 may contain toxic impurities along with soluble barium and aluminum. Her book, The Artist's Guide to Health and Safety, also has sections on the health hazards associated with barium, and we recommend consulting her latest work through her website.
This is used frequently in commercial oil paints, probably too extensively, as it is inexpensive. Some emerging lightfastness testing suggests that baryte may actually affect the lightfastness interactions with pigments, but more research will need to be done on that point. It's reasonable to also infer that it may be added to titanium white and (possibly) not be disclosed on the paint tube, as it is less expensive than titanium and may soften the qualities of titanium. It is also likely that it is added to a great many other colors without being noted. We appreciate where paintmakers call out its presence as it gives an artist more control over their materials. Barite can be useful for flesh tones and other areas where reduced tinting strength is useful. When used alone barite does have a propensity to yellow but it may affect the overall lightfastness, which is one reason we wish it were more widely disclosed along with the health and safety reasons.
In the Artist's Handbook, mentions that this pigment is actually fairly heavy, and so when it is used to as an inexpensive filler in paint, an artist may pick up the paint tube and mistakenly think it is highly pigmented when in fact it is filler. In fact, in industry terms it's a "weighting agent" which is funny to think about in terms of artists' oils-- the name Barite actually derives from the word for 'heavy'. More on barite from Natural pigments.
Something that is interesting is that barite has a range of paradoxical behaviors depending on the both the painting medium and the quantity used. The Artist's Handbook mentions that in oil it can enhance some opaque pigments' opacity, while in general just adding a little can also enhance transparency. The quantity matters as well as the application. In oil it's a transparent, dingy whitish grey, but it is so bright in water-based media that it is used for a white standard, like a reference point for brightest whites. In water-based media, it is used in gouache, which is opaque.
