Calfskin. Originally EarthTone started with goat skins, because they are thicker and more durable, but in 2010, after many requests ET decided to make the switch to calfskin. Although they can take a smidge longer to acclimate, the tonal qualities of the calfskin, hands down, outweigh the goat.
There is no denying that with a change of temperature/climate, there will be a slight change in the heads. That being said, if you have a set in your house or studio, after a couple weeks of stretching, the heads will settle nicely and just need the average tune up.
EarthTone heads are treated with a chemical (comparable to a salt cure) to help decrease the typical stretching and help them sustain different climates changes.
EarthTone are specifically designed like your standard Mylar heads so anyone can easily mount them. It is suggested to let the head sit barely tightened on the drumshell the first day you receive it. The next day it can be hand-tightened and tuned. If you are in the complete opposite climate of Florida (anything different than hot and humid 9 months out of the year), you can give it an extra day before tuning all the way to pitch. You will most likely need to retune the first week or so, but after two weeks the heads should settle nicely.
Yes, you can use it as a bass head on most bass drums. You’ll have to be very particular and cautious while you tighten the head down to make sure it is side-by-side or else the head can slip.
Unfortunately, at this time they only have the standard head sizes available.