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Re: wooden boards [ultramarine]

>Date:    Wed, 11 Jun 1997 03:35:45 -0400
>From:    Richard Minsky <minsky@xxxxxxxxxx>
>Subject: Re: wooden boards [ultramarine]

>Jack- those are two good clear posts! But how do you make the "real
>ultramarine?" I thought it was made by grinding Armenian Lapis Lazuli.

Richard, et.al.,

Grinding is only the beginning!  I crush lapis lazuli with an iron
mortar/pestle (the sulfur dioxide/egg fart smell comes from the pyrite
inclusions in lapis), then I reduce it further in a ceramic mortar and
seive it through finer and finer screens until it is a very fine powder.
Then I mull it on a sheet of glass until it is about as fine as talcum

Then I put the powder into a crucible, bring it up to a red heat in a kiln
and quench it in water to break it up into even finer dust.

Then make a gumbo of pine rosin (6 parts), gum mastic (3 parts), and
beeswax (3 parts); melt these together and stir in the lapis powder.  When
this is cold it looks like army green with a deep indigo cast to it.  After
a few days, warm it back up, add some lye and stir a little linseed oil in
(get the linseed oil by expressing the oil from the seeds of the flax
you've grown to get fiber to make thread/cord for bookbinding or
papermaking; just a thought).

As you stir this mess about the blue will begin dissolving into the oil/lye
mixture.  Pour this into a flask and continue working over the gumbo.

In the end, however well you work things, you will end up with approx. 4 %
of beautiful deep blue, the genuine ultramarine blue.  I work up three
grades of blue from the stone and have a bit of ultramarine ash (gray-blue)
left at the end.  Genuine ultramarine blue is very expensive; artificial
ultramarine blue is fairly cheap.  And it takes a microscope to tell the
difference.  If I didn't have to do something with the lye I wouldn't go
through all the trouble to make the pigment.  Probably.


Jack C. Thompson
Thompson Conservation Lab
7549 N. Fenwick
Portland, OR  97217


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