Motor Oil Or Kerosene In Clay Body?

[curt]

Was throwing a heavy iron commercial body today and noticed what smelled like motor oil in the clay. A potter friend said that sometimes in industrial clay operations they do put kerosene in the clay body to lubricate it through the barrel of a pug mill or extruder when they are producing bricks or other products. I also think I remember that modelling clay has oil in it, doesn't it?

 

Has anyone ever heard of this?

 

If there is some kind of petroleum product in the clay, it raises a host of questions.

 

Does it improve plasticity, or workability more generally?

 

Does it alter drying times for the clay?

 

Does it alter clay chemistry?

 

Do firing schedules need to be adjusted when such a product is in the clay?

 

Etc.

 

Any thoughts appreciated.

[Guest JBaymore]

I'd be a bit concerned about having my hands in contact with whatever petroleum product it might be if it was throwing clay. 

 

Most of that kind of stuff is quite aromatic... so a tiny bit will smell pretty strongly.  So that is good.  Likely not much there.

 

Maybe they use the same equipment to mix many different types of bodies.... and someone did a crappy job of cleaning the equipment?

 

best,

 

..............john

[Marcia Selsor]

in the 90s it was popular to spray WD-40 in to your extruder to make the clay slide better and for easier cleaning. 

Plastacine , modeling clay is not for firing but is composed of motor oil, wax and clay. 

 

As John says, a little would go a long way. I'd be a bit concern about firing in an electric kiln. Depends on how much and what petrol product it is.

 

Marcia

[neilestrick]

I seriously hope that they didn't put anything like that in the clay. I doubt that it would pass the non-toxic requirements if they did. And if they did it should be noted on the MSDS, and if it's not then they are in violation of the law. It's possible that their machines leaked a little oil into the clay, however if it happened in the pugger you would see it on the outside of the block. If it happened in the mixer I doubt that enough of it could have gotten into the clay to be noticeable. I doubt that they mix and pug oil based clays in the same machines as the regular clay. If they do then that's not smart because you'll never get it clean enough to keep the oil out of the other clay. I would call the clay company and let them know. They need to be aware of it if that's truly what is going on.

[glazenerd]

Curt:

My initial thoughts would be: it would weaken the green strength to some degree because it would not dry.

My larger concern would be the sulfur content of the oil. Oil has a fair amount of sulfides in it, even after being refined. Pending the levels, could create pin- hole issues that would not be easy to resolve.firing to cone 10 will get rid of the oil, but sulfides would remain.i certainly would be venting when firing: benzene, cadmium, few other nasties in oil. In the end, the sulfides will probably be the thing to bite you. All depends on the levels.

Nerd

[oldlady]

marcia, i have been using liquid WD-40 for years.  started with a gallon in the 1990s and still have about a quart left in the can.  it is used inside glazed pottery or metal or plastic shapes that hold the clay as it dries.  it evaporates long before firing and i use an electric kiln.  not a problem.

[curt]

Thanks for all the responses here.  I am running some tests on this clay and will report back if I find out more. 

 

So far I have not seen any actual evidence of oil (eg; oily residue coating the insides of buckets, pots spontaneously combusting when near a hot kiln, etc.)

 

I am also starting to wonder if the smell is somehow coming from the iron oxide in the clay.  I know that this clay body has 4.4% (oxide weight % pre-firing) of red iron oxide.  Any others smell this kind of thing with their high iron content clays?  Maybe I am mistaking that smell for oil?

 

It may also be relevant that this clay is rather fine grained as dark stonewares go.   Sieve testing indicates that 82% of it will pass a 200 mesh screen.  Also, residue on 100, 200, 325 and 500 mesh screens all look about the same color as what passes into the pan (ie, the remainder), which suggests to me that plenty of the iron is quite fine as well (whole clay body ball milled maybe?). 

[Guest]

Oil and kerosene floats on water, try breaking up some moist clay to small pieces and placing them in a container of water and see what happens.

[Mark C.]

Oil and kerosene floats on water, try breaking up some moist clay to small pieces and placing them in a container of water and see what happens.

Yes  try this-my guess is its not oil 

[curt]

The clay does not float if that is what you are getting at, nor can i see any oily residue or anything sticky like oil on the surface of water or containers. Increasingly thinking it cannot be oil.

[Guest]

The clay does not float if that is what you are getting at,

 

Nope, only oil

 

 nor can i see any oily residue or anything sticky like oil on the surface of water or containers. Increasingly thinking it cannot be oil.

 

Yup

[Mark C.]

This may be that new clay that self fires itself -you light it like self starting charcoal .

The newer cars use flex fuel and this may be the latest in thinking clay wise.

[curt]

LOL, that one is not offered yet where I live (as far as I know!). Will have to get some of that when it becomes available.

[Min]

No clue if this might be a possible direction of thought? (the coal bit or post #6)