Obernetter's Formula:
Dextrine 60 grs (grains)
White Sugar 75 grs
Ammonium Bichromate 30 grs
Glycerine 2 to 8 mins (minims)
Distilled water 3 oz (ounce)
Woodbury's Formula:
Gum Arabic 60 grs
Glucose 45 grs
Glycerine 10 mins
Potassium bichromate 30 grs
Distilled water 2 oz
Wall comments that formulas are usually given in British apothecaries
units. which are 1 oz (wt) = 480 grains and 1 oz(liquid) = 480 minims so I
presume that is what these are. He also states that chemicals are sold
according to a different scale in which 1 oz(wt) = 437.5 grains. I think
that the grains are the fixed units here and the ounce varies. Anyone know
for sure? This is where the UK and the Commonwealth list members come in.
As far as I know dextrine is not a single well defined substance but the
results of various modification processes applied to starch which itself is
different depending on the source. One easy process you can do yourself if
you can't find a commercial source is to spread the chosen starch on a
baking sheet and bake it. You will have to experiment with materials,
time, and temperature. The dextrine conversion is what goes on when cooks
make a roux by heating flour in butter or some other fat. As in a roux the
home brewed dextrine will be various shades of brown.
Wall is more specific and gives dextrine the formula C12H20O10. That end
is Oxygen 10. Wall also notes that the product can be made by heating
starch in the presence of a dilute acid. He describes it as buff colored
and also known as British Gum. You know you're done when the product can
be dissolved in cold water.
These are single solutions kept in the mixed state. Coated onto your
surface, dried, exposed through a positive, powdered,
Hope this helps.
Eugene Robkin
88At 02:05 AM 2/3/98 -0500, you wrote:
> Since it has been brought up, does anyone have a good formula for a
>simple dusting-on process? Mine doesn't seem to work well:
>
>Pt. A: 28 ml honey
> 30 ml gum arabic
>
>Pt. B: 30 ml ammonium dichromate (saturated solution)
>
>2 parts A: 1 part B, coated on paper and exposed under a positive.
>Develop by blowing hot air - unexposed areas become tacky and accept
>dusted on pigment, human remains, etc.
>
>Thanks,
>
>Dan
>
>
>