Yup. The "women's" I have states potassium alum. That was the only reason I purchased it. I have a RazoRock alum block and before purchasing the crystal deodorant stick I checked to verify the type of alum - potassium.
Initially in my foray into the SR realm, I tried the fingertip alum application in order to make skin stretching easier. But I found after a number of shaves, it (the extra step with alum) wasn't really necessary.
The feedback is why I recommend Alum to newbies. Pain is a powerful teacher, it's immediate, and it's not subjective. My skin is more oily than dry, so Alum remains my front line astringent, in lieu of witch hazel.
I use the block occasionally but have had really good luck with finely powdered alum mixed into my bottle of witch hazel. Just gotta give it a good shake first.
The stinging sensation is great feedback. One of the reason I recommend an alum block to all beginners... and it's cheap as hell to boot! I still use it after every shave as I find it helps a lot with keeping my sin clear of the remaining bits of acne I never got rid of from my teenage years.
I just picked up my first Alum block. I've been wet shaving 5+ years and have yet to try one out. I do love my Witch Hazel, but I want to see how this will preform. And from this thread, it looks like Alum does have a long-life for many shaves.
The few times I've needed it, the combo of a heavy spray of WH immediately followed up by the dry block rubbed on the WH has had an excellent effect.
Alum will let you know how you performed as well. I experiment with different blades or types of razors so my results vary. The past month has been mostly Gillette Fat Boy shaves. I can tell when a blade doesn't agree with my skin by the heat from the alum. Considering it's your first time, use a razor that you know well. The report from alum will be spectacular if your technique is off.
I too am an alum block user. Apparently they are sold at Indian grocery stores. I have one a few miles away. So when my current block gives up the ghost, I'll check it out.
I was only using one side of my block. The other side developed sharp edges and got kind of crystallize. A little running water and rubbing with my thumb smoothed it out. Now I use both sides after every shave.