Sigma Power Select II, #240, first impression
To add to Clinton's post earlier ...
This stone is intended for hard steel and is all that Schtoo has said about it.
I got it primarily for lapping blade backs to get them flat fast.
Tested on a 1" Titan firmer and a similar chisel (3 clover leaves on the back, can't read the maker's name, but damn hard steel).
Frankly, given my experience of ceramic whetstones, I found this comically odd.
Talk about soak up water, and leak it while in a holder, and see the water bubble up on the trailing stroke of the chisel.
But, it produces a nice paste quick smart and cuts at the same pace.
The Titan was rubbish on the back so I took the worst out by jointing the edge on a bench grinder. About 4 mm off. Then 10 mins on the Sigma and the back was flat to maybe 25mm back.
The clover leaf brand looked an easier job to begin with but it had been rehabbed and there was dubbing over about 3mm back from one edge running on the diagonal to the other corner.
10 mins on that and I had to step back to a #120 ceramic whetstone, and then return to the Sigma.
Next time I'll try Schtoo's advice to add some SiC grit to the #240 stone.
What needs attention with HCS and this stone is to clean and dry it carefully since any remaining steel oxidizes rapidly.