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I'm using an old Venco de-airing pugmill to reclaim porcelain clay. This style pugmill has stainless steel screens that turn the clay to spaghetti just before the de-airing chamber. There is a small vacuum chamber on top, with a plexiglass lid and gauge. The vacuum pump sits on the floor and connects to the vacuum chamber by a hose. There is a slot at the bottom of the vacuum chamber through which air is drawn away from clay in the barrel. It's normal for some clay to be sucked up through the slot. The manual says it need only be removed if the chamber becomes full. The kPa on the guage should be high- btw 95-100. Okay, so I'm actually getting that peak of 100 kPa for the first time. Difference could be that I used a caulking as a gasket this time. BUT, it flutters quickly down to 60 then climbs back up on a regular basis. This will happen even if only the vacuum pump is running, and the pugmill is not. It seems to be more frequent the LESS clay there is sucked into that vacuum chamber. It was staying pretty steady yesterday but I thought the chamber was too full and possibly the main area being de-aired, so I pried up the plexiglass and cleared the chamber. It was quite difficult to get the suction high again, and the frequency of fluttering is still increased today (I can't seem to post a video, but it's several times a minute now). My question is, is this normal? I'm curious why it's happening. I've no idea if I could buy a separate vacuum pump that would be suitable for the pugmill, but maybe that would be worth considering. At the same time, the clay seems to be de-aired well enough. It's not as good as boxed, but probably the best reclaim I've had, so there's that. Also, can anyone suggest a putty-type product to use as a gasket, that would be both low odour, and easy to remove when necessary?
Dear colleagues, I have to make a decision as I could have a Venco Super Twin in a few days here in my studio what would normally take months to be delivered and I have a big order of lots of plates to throw. In my research about pugmills I have come as far as that I think I have to decide between buying a Peter Pugger vpmss20 and a Venco Super Twin, both stainless steel and de-airing. I throw porcelain and run a studio production, means around 2 tons a year, getting more (sorry, I'm not a native speaker)... I'll need it in the first place for replacing the wedging of new porcelain clay as I find this extremely power- and timeconsuming for production. I let the wet material dry a little bit down to have a stiffer clay for throwing thin bigger pots. That means the clay has stiffer parts outside from the drying and softer ones inside even if I dry it slowly under a soft fabric to avoid too fast drying. I hope such a machine could mix and de-air it for having a homogen porcelain body ready for throwing. That's what I intend mainly. To reclaim crap is also an idea but not really important as I can sell trimming crap for a small money to someone who re-uses it for small sculptures. i know in stoneware de-aired clay is a gorgeous thing for throwing, but porcelain is different and it seems to absorb air whenever possible so the vacuum effect might be a problem? What I have heard about the Peter Puggers: Some potters have problems with porcelain coming out with no plasticity. Also heard a rumour that the pugging chamber of the PP is too short for good de-airing. The advantage of PP seems to be that the clay can be stiffened or dried down easily and that any stiffness doesn't seem to be a problem at all as the mill is very strong so it won't stop with stiffer clay. About the Venco: the twin spiral shall have a quite well mixing effect but the de-airing pump shall also not be so good. Another disadvantage of the Venco is that I heard it stands still if the clay is too stiff and you have to open it to pull the clay out before going on with softer clay. I'm afraid I will have spent so much money to have small air bubbles in my fired ware what must be quite horrifying and / or that I have a machine that stops when i put a bit stiffer clay for bigger pots into it. It would be SO GREAT if anyone working with porcelain with these machines could share his/her experiences... thanks so much, claude