Tip #75  About Pug Mills and Clay Mixers

I've been getting a lot of questions lately about pug mills, so I thought it would be a good time to discuss them. Here are the frequently asked questions and my answers. Please keep in mind that not everyone might agree with every part of each answer. I have talked to many people about pug mills, and I hear a lot of different opinions. Even getting someone who makes pug mills to explain exactly how they work is not really easy; there seems to be an element of black magic involved. So my answers are based on talking to many people and blending the many opinions.

Q. Do I need a pug mill if I don't mix my own clay?

A. Many people who buy pug mills do not mix their clay from scratch. 

Some run their clay through the pug mill to make it easier to throw. Their clay may be a little hard and they soften it some in the process. But even without adding water, wheel throwers in particular say the clay becomes easier to work with after running it through the pug mill.  When clay sits in a bag, it tends to dry out unevenly, and re-pugging evens out the moisture levels. It also realigns the clay particles which makes throwing easier. 

Of course this can also be accomplished by wedging the clay yourself. You have probably seen that experienced potters usually wedge their clay when they take it out of the bag. Basically, running the clay through the pug mill takes the place of the wedging process. And it is much easier on the wrists. This is particularly important for those who throw a lot of clay or are older.

Another very common reason people purchase pug mills is to recycle scraps. (More on that later)

Q. Do I need a de-airing pug mill?

A. De-airing pug mills use a vacuum to suck air out of the clay. When you buy pugged clay (anything you buy which is pre-mixed in 25# bags), it has been de-aired.  It seems that only wheel throwers want clay that has been de-aired. And many of the non de-airing pug mills on the market today mix the clay with very little air even without a vacuum. 

Vacuums do tend to dry the clay out a little. And some potters don't like them because the vacuum is one more thing to break. But if you have a de-airing pug mill, the vacuum can be turned on and off as desired. 

The majority of pug mills we sell do not have vacuums. However, we do sell a number of Shimpo PM071's which can have the vacuum added later if desired.

I remember asking this question to someone who has made clay commercially for many years.  I asked if I should get a pug mill with a vacuum or not.  My main complaint was that I didn't use my clay fast enough and it was too dry.  So I would usually re-wet it, re-wedge it, and throw with it (see Tip #1).  He told me that if I was happy throwing with clay that I had re-wet and re-wedged, then I did not need a vacuum because non de-airing pug mills were certain to be better than what I was doing myself.  Good advice!  

Q. I want to recycle scraps. Do I want a pug mill, or a mixer/pug mill like the Shimpo PMX-060? 

A. All pug mills will recycle scraps to some degree. The benefit of a mixer/pug mill like the PMX-060 is that it allows you to recycle scraps more easily.

Most pug mills require you to "pre-process" the clay to get it to a relatively tight range of consistency before going in. Not too wet and not too dry. If this isn't done, then the clay can go right through the pug mill without really being blended. With a mixer/pug mill, you can add scraps of many consistencies, wet, dry, etc. into the hopper, mix, then add water, more clay, or dry clay as needed until you get to the right consistency, then initiate the pugging process. 

Q. What if I want to mix my clay from scratch?

A. Some people do want to mix clay from scratch, especially if they have a special recipe. Usually this is fairly high volume and you would have a separate Clay Mixer and Pug Mill. For smaller batches it is possible to use a combination mixer / pug mill.

In Summary:
A pug mill is not one of the first pieces of equipment a studio potter or even a school gets. But if you are throwing a lot of clay and want your body to last longer (especially the wrists), or if you generate a lot of scraps that you would like to recycle, then you may be ready to add a pug mill to your studio space. 

Copyright 2006 Cindi Anderson, BigCeramicStore.com   May be reprinted if credit is given.