[pure-silver] chemical purity
- From: "Koch, Gerald" <gkoch02@xxxxxxxxxx>
- To: "'pure-silver@xxxxxxxxxxxxx'" <pure-silver@xxxxxxxxxxxxx>
- Date: Wed, 5 Jan 2005 10:59:59 -0500
How pure are the chemicals your are using to compound your developer? I mention
this because there have been some comments recently about fog with certain
formulas.
Commercial grade triethanolamine can contain 15% diethanolamine. This will
raise the pH of developers made with it above what would be expected. This can
cause higher fog levels and contrast and density problems. Diethanolamine has
an ammonia like odor and its presence should be easily detectable since
triethanolamine should be odorless. If you have any doubts about the purity or
are experiencing problems you might also ask the supplier. BTW, the grade
supplied by The Chemistry Store is 99% pure.
Another chemical where source is important is ethylene or propylene glycol.
Using antifreeze as a substitute is not a good idea as it usually contains other
ingredients (such as rust inhibitors) which may not be photographically neutral.
One should always be careful when using any technical grade chemical for
photographic purposes. Test any new supply thoroughly before using it for
critical photos.
Some companies such as Arm & Hammer and US Borax post MSDS's for their products
which are very useful for determining suitability for photographic purposes.
Check for iron and other metal impurity limits.
Jerry
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