iandol on sun 1 dec 02
Got a little bit further along the way today.
Because I was not getting an indication with my spot test on the vinegar =
in which the barium glaze specimen tiles had been soaking for four days =
(which might have been interpreted as there being no reaction between =
the glaze and the vinegar) I decided to evaporate the solution and =
increase the concentration of any dissolved materials. So I reduced the =
500 mls down to a small amount and brought the volume back up to 50 mls, =
giving me a multiplier effect of 10 to 1 in concentration.
Using a 0.1% spot test comparison solution (1 gm Barium Carbonate =
dissolved in vinegar and brought up to 100 mls, then diluted 1 to 10) =
showed that there was a similar concentration in the glaze test =
solution. The density of the precipitates were very similar.
This seems to suggest that during the exposure to this acid those glazes =
formed a solution which contained Barium ions equivalent to =
approximately one hundred parts per million of Barium carbonate. (If my =
rithing is good!!)
This result should only be regarded as an indication and not as a =
These were, for the most part, transparent glazes. I would like to test =
the recipe with the highest proportion of Barium Carbonate (which you =
may recall had 40% BaCO3 yet is a fully mature, if somewhat crazed, =
transparent glaze) separately. I would also like to test some of the =
Barium and Barium Copper Matt glazes (The latter being a chemical =
challenge because of the need to separate the copper ions from solution =
before measuring the barium ions)
More tests should be done. I would like other people to try to do this =
sort of thing.
Any interesting comments would be appreciated.
Ivor Lewis. Redhill, South Australia.