Hi Brittany Man.
Unfortunately I can not give you any information regarding the effects of Butter of Antimony (Antimony Chloride) because I have never added it to a finishing oil, my preferred method of finishing a stock is to apply the colour directly the wood be it either Alkanet Vandyke Brown artists colour, or sometimes Potassium Permanganate. Then fill the grain and finally apply the finish because I have found that if I apply a coloured or a finish that will colour the wood in some way it always well in my case it does, turn the stock colour patchy in the extreme.
I can only suggest that a little experiment is needed using Antimony but as I have said if you obtain the correct stock colour before you apply the finish there is really no need to apply a finish that will darken it further.
