Clay releasing from Hydrocal bats

[CactusPots]

I posted a question earlier about my hydrocal bats releasing clay.  The 2 commercial clays I use are Amador and Soldate 60.  The recycle from those 2 won't cleanly release from the bats even when much drier than you'd expect.  The Amador and Soldate will release when the bottoms are still soft.  I called Laguna and asked them what they thought about that. Their reply was that their commercial pugmills develop twice the vacuum the Peter Pugger can.

Anyone able to fill in the corners of this explanation ?  Exactly how would that make a difference?  Wouldn't pugging soft and then aging the clay give me about the same thing?  I'm mainly pursuing this as an avenue to learning something about clay.  I have perfectly fine uses for the recycle clay in throwing large pots that are wired off and handbuilding.

[Fred Sweet]

Cactus-

I’m wondering if some of the body fluxes in your clays are soluble enough, that when you rehydrate your scraps, they are attacking the plaster of your bats and thereby causing the difficulty in removing your “reclaim” pieces. It’s something that happens occasionally with casting slips. Mark C might be one to address this issue since he has more experience with casting than I.

Regards,

Fred

[CactusPots]

My question went directly to the guy at Laguna that formulates the clay, I am told.  My recycle is largely solid trimmings, very little to no bucket slop.  I've had the some of the same bats for more than 15 years, they don't really show any wear on the throwing surface.   Hydracal is very hard.   It does seem to me that the commercial clay is "tighter" than my recycle.  I haven't tried pugging clay right out of the bag.  I'd like to hear Mark's opinion on this as well.

When I'm pugging clay I typically run the vacuum up past the 15 on the outer dial.  Laguna said that  their pugmill is 50 HP and they can pull 29 inches of mercury and that a perfect vacuum is 30.  That being the case, there has to be some difference in the clay, I think.