Emotions and opinion run the gamut when it comes to utilizing denatured alcohol within the collodion process. Some suggest it should be avoided at all cost while others report you can pour with confidence. Both opinions have merit.
The first realization must be the understanding that the majority of collodion photographers today gain their information from social media channels originating in the United States of America. Therein lies the crux of the issue: what holds true in the good ole US of A may not be compatible with other countries, and most likely isn’t.
Most countries have liquor/spirits legislation that controls the manufacture and distribution of alcohol(s) and is taxed accordingly. Each individual governing body will have statutes and regulations; rarely are any two alike. This is why one might be able to acquire Everclear in one state but not in another. Everclear is not distributed to other countries – full stop -- but may be imported as a special order item through the local liquor control board. The final retail price will reflect the special order.
Should one be inclined, a quick internet search will show the distillation process produces an alcohol that also includes methanol. Due to being poisonous this methanol is separated, what remains is a consumable alcohol spirit (aka Everclear) that is controlled and taxed by applicable governments.
Being Canadian, I will only speak to Canadian government regulations. In order to make the spirit alcohol denatured the producer must add a denaturant to render the spirit as a non consumable. There are dozens of denaturants –ranging from almond oil to vinegar—that can be added depending upon the final use. The net result is 14 different grades of denatured alcohol depending on the additive that was introduced.
The bottom line is the collodion photographer requires a denatured alcohol grade identified as DA-2A. The additives in this grade of denatured alcohol are methanol and ethyl acetate; both are additives that are naturally occurring in the distillation process -- consequently are only being reintroduced.
Should this all sound confusing, it isn’t really. The distiller is simply adding what has already been removed following the distillation process.
For more clarification and further reading please refer to https://laws-lois.justice.gc.ca/eng/regulations/sor-2005-22/FullText.html . When one realizes there are 14 grades, and many, many more denaturants can be used it is little wonder the hardware store variety has generated so much, and rightfully so, disconcerting information.
In Canada, DA-2A denatured alcohol can be used in all facets of collodion photography with confidence. Photographers in other countries will have to do their own research and testing.
The answers lie within the Safety Data Sheet of the product that might be considered.