Ask the Experts
What is the ingredient co-precipitate?
Ask the Expert: “I noticed that some of my non-Utrecht paints list “co-precipitate” as an ingredient. What is “co-precipitate”? Is it a traditional paint ingredient?”
A: Co-precipitate refers to how a pigment or filler is produced. A precipitate is something that condenses out of solution. Precipitation is a chemical manufacturing method which starts with a liquid into which raw ingredients are dissolved, and the desired product (in this case, pigment) forms as tiny solid particles which can be separated and collected.
Co-precipitates are products that condense or fall out of the same solution together. Barium sulfate, for example, is a co-precipitate of cadmium pigment in cadmium-barium colors where both pigment and filler are made simultaneously in the same solution. Because barium is a colorless filler (an inert solid which replaces more costly pigment), cadmium-barium colors have lower tint strength and less covering power than more expensive, pure cadmium colors, which are produced without co-precipitates.
Chemical precipitation of pigment was originally referred to as a “wet process” because it used a liquid solution, unlike other processes involving the corrosion of solid metal. Lead white, for example, was historically made through various techniques of inducing white corrosion, which was scraped, abraded or tumbled off the metal substrate, and collected as pigment. These earlier processes often made it difficult to extract a high percentage of finished product, with some half-processed material present. The resulting pigment was uneven in particle size and could contain impurities affecting performance in paint. Chemical precipitation is very efficient by comparison- a high percentage of raw material is converted into the final product. Precipitated pigments generally have a tiny, uniform particle size and a high degree of purity. This degree of fineness and consistency makes it possible to produce paints that have exceptional smoothness and potency of color, with much more reliable drying rates and overall performance.
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