What is “Setting Powder”?

Setting powder is simply citric acid, C6H8O7  (3-carboxy-3-hydroxy pentanedioic acid):

It can also shown like this, for those who are more three-dimensionally inclined:

What is Citric Acid?

Citric Acid is a weak organic acid, similar to vinegar, but is commonly available in a dry, solid form instead of solution. It is odorless, and, at room temperature, citric acid is a white crystalline powder.  It is sold for use as a food additive (it imparts a sour taste), and for use in water softeners and natural cleansers (it chelates metals).

Citric acid crystal under polarized light, enlarged 200x

Citric acid occurs naturally in citrus fruits; lemons and limes have particularly high concentrations of the acid; it can constitute as much as 8% of the dry weight of these fruits.

In biochemistry, it is important as an intermediate in the citric acid cycle (aka Krebs cycle) and therefore occurs in the metabolism of virtually all living things.

Citric acid was once produced primarily from citrus fruit. Industrial production today utilizes cultures of Aspergillus niger which are fed on a sucrose or glucose-containing medium to produce citric acid. The source of sugar is corn steep liquor, molasses, hydrolyzed corn starch or other inexpensive sugary solutions. After the mold is filtered out of the resulting solution, citric acid is isolated by precipitating it with lime (calcium hydroxide) to yield calcium citrate salt, from which citric acid is regenerated by treatment with sulfuric acid.

How is Setting Powder utilized in pysankarstvo?

Setting powder (citric acid) can be used as an alternative to vinegar (acetic acid), especially by those individuals who don’t like the sour smell of vinegar.  It works in a similar fashion, by acidifying the dye solution to improve adherence of the aniline dyes.  It is neither better nor worse than vinegar (acetic acid) for this purpose. 

Setting powder is used the same way vinegar would be used, and in the same circumstances.  A pinch is added to a jar of dye solution in lieu of a tablespoon of vinegar.

What are the advantages or disadvantages of Setting Powder over Vinegar?

The differences between the two are minimal.

The main advantage of setting powder (citric acid) is aesthetic.  It does not have the sour smell of vinegar.  It can also be more convenient, in that you you only need to keep a small packet of it around instead of a big bottle of vinegar.

Disadvantages include more difficulty with titration–it’s easy to add too much citric acid, because only a grain or two is really needed.  And, because it is odorless, it’s not always obvious if you’ve added (or forgotten to add) citric acid to a dye solution.

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