The updated recipe
Brandy (cheapest brand possible) 44ml
Sandarac 2 gram
Benzoin resin 1 gram
This is something of a famous first. No need to substitute any of the ingredients and the original recipe has measurements for everything. So it was very simple to just pare it down to a suitable test sample. I grounded the resins before pouring it into the brandy. I used a small jar with a lid. After that I just shook it every time I passed it until a week had passed.
Both Sandarac and Benzoin are soluble in alcohol, but though I can’t find any information on how strong the alcohol should be for the Sandarac, Benzoin is generally recommended to be dissolved in 80% alcohol, dissolving even easier if you warm it a little. Brandy is about 40% and this recipe says nothing about warming the solution either. The Swedish pharmacopeia of 1775 recommends 50% alcohol in a ratio to 6 parts alcohol to 1 part Benzoin. Let it stand for three days and strain though a paper. (Source) A recipe with both stronger and more alcohol than the recipe I used.
Benzoin resin
Source: therapyangels.com via Elisa on Pinterest

