Friday, 23 February 2007

Fun with lakes

recovered from my corrupted 'Experiments with colour'

For the last few months I have been experimenting with producing a variety of lakes from brazil wood using known recipes going as far back as the 14th century.

Mostly the results have been quite predictable, in that an alum based with wood has yielded a cherry red lake. Chalk precipitates of this have given a range of opaque colours going from pale cool pink to almost purple, this is dependent on the acidity of the lake and the amount of chalk ground in.

The best thing about scraping chalk into the lake is that it decomposes, ie does not retain much of its structure as it combines with the alum and the brazil colouring. Upon drying it is easy to grind any of the few granules that are left.

On top of this I have been trialing making transparent precipitates using caustic soda solution as a substitute for wood ash lye, mainly for my own convenience. Initial results were poor as I had made a far too alkaline solution and it resulted in a colour that corroded the paper substrates.

The solution strengths are under review.

Also coming up will be weld and madder lakes, again close attention to the alkali levels in the soda/lye water. Medieval methods of testing optimum concentration were to see if an egg floated in it and did not corrode the shell. This method seems fair enough.

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