I am not sure that it matters. I bought the cold pressed and it was about 15 bucks at Amazon.
The issue with castor oil is that you are unlikely to be able to tell whether it is worthwhile or not, especially if you have other meds in your protocol. If you have diffuse thinning and not a bald scalp, then using Castor oil for micro-needling is probably not a good idea as you will pull many hairs out which is excruciating for the balding. Just use it as a conditioner and leave it in an hour or two or even overnight.
I don't think that Castor Oil would be good as a carrier because it is extremely sticky compared to most vegetable oils and much harder to work with and then even to wash out. But you could put it on right after or you could ingest a tiny amount daily, both of which I have done but for me, this is a non-essential treatment which I have tried out to try to provide feed-back to others. If you can use minoxidil, then use that.
Janey's rule of thumb is never try to re-invent the wheel if your goal is actually to regrow hair. I tell the "just in it for the hair" HRT guys this but it never gets through. Pick something as a protocol that you can more or less verify that worked for someone else and then copy that protocol as closely as possible and except for titration, don't change it.
@bridgeburn was growing tons of hair out from baldness but essentially, none of the guys who used their own protocols had positive results unless they were very young. The difference was that
@bridgeburn knew what he was doing exactly while the other guys were making adjustments to try to avoid breast growth and the adjustments were not effective in terms of regrowth nor most likely in avoiding breast growth since few cis-males understand how menarche functions related to hormonal levels.
