Plaster casts are of the obv.
only. So you need two of them for each coin, which actually has great advantages for study: there is no hidden side
needing to be turned over, you can write information about source, weight
, die number on the blank back, and you can separate the obv.
from the rev.
in order to do your die comparisons with like designs, the obverses on the one hand and the reverse types
on the other.
All sulphur casts that I have ever seen have both sides on the same cast
, just like the original coin. I believe Mionnet
's sulphur casts were all black, but Captain Smyth
's are green, red
, yellow, the better to imitate the original patinas on his Roman sestertii
. So a collector might prefer sulphur casts, they're much more like the original coins.
For study purposes sulphur casts are awkward, again just like the original coins. The student will want to make plaster casts or photographs of the originals, in order to be able to conveniently study them, and for the same reason he will want to make plaster casts or photographs of any sulphur casts he comes
I don't know how sulphur casts are manufactured. Mionnet
's original molds turned up some thirty years ago and were supposed to be published by a team including Maria
Radnoti-Alföldi. If that book ever appears, hopefully it will explain to us how sulphur casts were made.