Is it necessary to take off the skin and spines if one is drying the cactus in preparation for an extraction?

No, its not necessary. It is removed generally because some people believe the skin and spines may cause nausea when eaten/brewed into tea, along with the woody core. I dont think it will cause any problems with an extraction.

That's is what I had heard, and also what I was thinking about. Why throw anything out if you're doing an extraction?

You could even leave the woody core in the powderized mixture..... I believe phlux managed to extract a small but significant amount from a handfull of cores he had lying around....

I see those arguments allot... How about the other way around?
- The stuff you dont put in there wont 'yield' unwanted molecules: no extra problems when purifying..
If you can already get rid of some unwanted material before the extraction, then why dont you?
I see it as an optimalisation (preparation) of the extraction. JUST TO MAKE SURE

lol. If there where still roots on the cuttings, would you leave them too?

Also i like the excercise in patience (deskinning the cactus, and separating the green flesh). It adds to the 'ritual' and mindset. It reinforces my determination and focus to do this. But yea, thats just me trying to be spiritual ; )

Would be interesting to see an extracion on the white flesh, or woody core.
Just to see if it really yield (more) mescaline, or if it just makes washing difficult (in the end yielding less mesc due to loss during washing)