Ultramarine Pigment Safety
Ultramarine Pigment and Ultramarine Rose Pigment Safety – some special advice for artists and hobby paint makers
Ultramarine Pigment and Ultramarine Purple / Violet / Rose Pigment Powders;
these pigments are commonly presumed to be
nontoxic and stable (and advertised as such),
yet the molecular structure is very unstable and reactive, under a variety of circumstances.
——- hydrogen sulfide danger ! ——- this rare and very unusual gas,
when inhaled during paint mixing, can cause paralysis, and may be lethal
even at moderate concentration (from 100ppm). …even a single inhalation of this gas may be life threatening to the artist.
The various ultramarine pigments have become very popular with artists wishing to make their own paints. Both ultramarine and ultramarine purple / rose pigments can safely be mixed with linseed or walnut oil by artists in their own studio. This is not thought to be of concern, as the oil safely encapsulates the pigment grains.
But both ultramarine and ultramarine purple pigments should not be mixed with aqueous binders and mediums without special precautions. Confusingly, the dry pigment powders are considered relatively safe, and are classed as ‘nontoxic’ in sds documentation. Even these dry powders by themselves may emit sulfuric vapors, depending on conditions and the chemical composition of the product used.
Yves Klein, Tree, Blue Sponge Object from 1962,
Yves Klein died shortly after making this piece, aged 34
In practice (as we know from first hand experience), mixing any kind of water based paint —- with gouache, acrylic, or watercolor binders —- in an artists studio from ultramarine pigments (synthetic or as mineral Lapislazuli) is strongly advised against, as it can cause the production of very dangerous gases.
The complex molecule of lapis-based powders is known to contain large amounts of unstable sulfur atoms within their matrix, which when liberated, for instance through the addition of trace amounts of lead, hydrochloric, or any other acid or alkaline, can easily produce poisonous gases with a rotten egg smell which are poisonous and in higher concentrations can even be lethal through inhalation, while mixing paint.
(note: a sulfuric smell is not always present or noticeable).
In order to make this mixing process manageable and safer for artists, a ventilated / extracted fume hood would need to be used while paint mixing, and a face mask with inorganic active carbon cartridges also needs to be worn, as a minimum precaution. However, once mixed, the paint should be stable and without further emissions.
Overall, it is recommended to use ready mixed, shop bought, ultramarine paint products in preference to mixing it yourself. (see below)
the pigment industry is aware of these emission issues and internally refers to the problem as ‘the unreacted sulfur problem’ within the synthetic ultramarine ‘chromosphere’ (molecule) that is being synthesized during a complex, sulfur rich, manufacturing process that mimics the natural formation of lapislazuli rocks and minerals
illustration of a typical lapis lazuli or synthetic ultramarine
molecule (chromophore); natural and synthetic variants are considered
almost identical. Lapis (Lazurite / Azurite) is considered one of the most complex minerals found in nature.
GUIDE:
black —- Si4+ / Al3+ | yellow — Na+ | green — S3-
the abundance and surplus of sulfides is clearly visible, and this accounts for the latent potential for toxicity
Ultramarine pigments and sds safety data
Seven samples of sds sheets from different manufacturers and countries (safety data sheet) for ultramarine pigment powder. Some give adequate information about hydrogen sulfide risks; most products and their sds sheets, however, especially by US vendors, do not include what we believe to be essential information.
LEAD: Some ultramarine pigment compositions also list lead as an ingredient; lead is a catalyst and will exacerbate the risk of poisonous emissions during paint mixing.
WHAT ABOUT FACTORY MADE ULTRAMARINE PAINTS… ARE THESE SAFE?
Ultramarine Paint and Ammonia
Considering the real and present danger posed by ultramarine pigment powders, the question arises if ready mixed waterbased paints, such as ultramarine acrylics are safe or not. The many acrylic paint manufacturers not only assure us of the safety of the ultramarine paint tubes, but also invariable place a ‘nontoxic’ symbol on the tube.
Looking at the basic chemistry involved when adding water to ultramarine acrylic, however gives cause for possible concern. Almost all acrylic paints contain significant amounts of ammonia, and this can often be detected by smell. Some products even contain a large amount of ammonia, as any acrylic painter will testify.
The ultramarine chromophore molecule is largely constructed from aluminum and sodium atoms that create ‘cages’ within which large amounts of sulfide atoms are loosely trapped.
But both aluminum and sodium atoms are known to quickly dissolve in ammonia solution, possibly in a heat-generating exothermic reaction.
Given these basic facts, it seems highly likely that at least some kinds of acrylic paint (e.g. those with high ammonia concentrations) are likely to produce poisonous hydrogen sulfide emissions during paint mixing and application by the artist.
There are also anecdotal reports of artists working with large amounts of acrylic paint who became unconscious while working, which may well be consistent with undiagnosed hydrogen sulfide poisoning.
CAUTION IS ADVISED!
Best, always wear a mask with active carbon filter and always ensure good ventilation.