clay Foreign Contaminates in Clay

[Ceramic Human]

I order from a clay company that shall remain nameless (cough cough.. columbus clay).  Every few weeks or so we will find a rubber or plastic chunk in the clay we receive. A few times in the past few years we have even had potters "find" metal shavings in the clay while they are throwing. . Once or twice this has resulted in a minor cut.  We took precautions to minimize the possibility that contaminates come from us. Moved all unrelated work out of the clay processing area, checked that the clay processing tools were not coming off in the clay, created clear signage for what does or doesn't belong in certain reclaim buckets.  Some pieces have been found before we process in the pug mill(straight from the supplier), others after. It's hard to know whether it's us or the clay company. There's some urgency to this issue for me because it could have been much worse. As experienced potters, what is your experience with clay companies. Is this normal? Should I shop around  for another supplier(despite a new clay body creating a  potential nightmare)? What actions would you take to prevent this from happening again? What additional precautions might we take in our clay mixing area?

[oldlady]

cannot remember a single incident other than the manganese lumps instead of speckles in a standard clay batch.  they replaced 16 boxes when i told them about it.  that was in the 1970s.

[JohnnyK]

I've been using various blends of Laguna Clay for more than 10 years and have never found contaminates in any of their stuff. I would guess that you have notified your supplier about your finds...what has been their response?

[Min]

I used a Laguna clay from their west coast plant for about 15 years, it would go through periods of having debris in just about every bag. Pieces of wood and rusty metal for the most part. I got tired of picking it out, finding it while wedging etc. so I gave up on it. This was going back about 8 years or so, might be better now.

[neilestrick]

If there is metal in the clay, it's coming off one of the machines, either your pug mill or their pugger or mixer. About once a year I will find little shavings in my porcelain, but they are never large enough or plentiful enough to cause a problem. If there are other things like rubber or plastic, those are being dropped in somehow, maybe from the scrapers they use to clean out the machines. Can you identify any of the rubber/plastic pieces as tools you use in your studio?

[Mark C.]

Laguna goes thru spurts of this- Its been small rocks -sometimes metal (very small pieces) and wood mostly-one it was cualking,now they are down to just one industrial pug mill for all bodies-the second one needs repair I heard and has been down for many months. So all bodies are going thu one mill-.I am going to ordere in a few montsh so we shall see. My last years order (12 tons) has been so so on contaminants .I think more about the crew doing the mixing vs materials that are dirty but thats just theory . Many materials can have them in them before the clay company makes the clay from them.

[liambesaw]

Never had anything come that way from Seattle pottery supply, but I've accidentally wedged things like twist ties, dog hair, canvas, name stamps, etc into my clay.  That's always fun

[Ceramic Human]

2 hours ago, neilestrick said:

If there is metal in the clay, it's coming off one of the machines, either your pug mill or their pugger or mixer. About once a year I will find little shavings in my porcelain, but they are never large enough or plentiful enough to cause a problem. If there are other things like rubber or plastic, those are being dropped in somehow, maybe from the scrapers they use to clean out the machines. Can you identify any of the rubber/plastic pieces as tools you use in your studio?

We haven't been able to make connections between our tools and the most materials we find. Here's a photo from a recent batch unopened from the supplier.

[neilestrick]

@Ceramic Human Is that a chunk of dried clay or something else?

[liambesaw]

Wow that's awful, no QC there?

I'd send it back, that is a huge chunk of plastic

[Ceramic Human]

5 minutes ago, neilestrick said:

@Ceramic Human Is that a chunk of dried clay or something else?

It's caulk. When I called, they said they had recently put back together their pug mill and that our order was one of the first batches to go through. They also said something about a screen in the pug mill.

 

6 minutes ago, liambesaw said:

Wow that's awful, no QC there?

I'd send it back, that is a huge chunk of plastic

I'll be doing that for sure.

[graybeard]

Never happened to me, I use STANDARD CLAY ^6.  (can't remember the number)

Take care

Graybeard

[Mark C.]

Caulk is bad news-makes it unusable-I had a friend with a ton of caulked clay-Laguna sent him a new ton

Caulk can squeeze thru some larger screens as it flexible

[Pres]

I have been using Standard Ceramics for since the year I took over, 1975. NEVER had anything but great clay, great service and friendly cooperation for all of my stupid and not so stupid questions. Still love working with them and will not move my orders elsewhere for those reasons.

 

best,

Pres

[Benzine]

I have always used Continental Clay, for my classroom.  I have never come across any debris, in my clay.  They do come with complimentary mold though!

 

The only time, that I've run into bit of "Other things" in my clay, is because the students weren't careful, when reclaiming.  I've found bits of plaster, bits of wood, gum, chamoises and even a needle tool...

Talked to a colleague, at a nearby District.  They had an issue with a student putting razor blades, in the reclaim.  Luckily, it was caught before anyone was hurt!

[liambesaw]

I think we all went through that 'razor blade in the reclaim' phase... Ah to be young again

[Pres]

Metal ribs were my downfall, cut up my left hand while centering, piece was about as long as needle and twice as thick as one. missed it in wedging some way, but then I was a newbie. .  not to be your again!

 

 

best,

Pres

[Mark C.]

The most odd thing I ever had was a cat turd in a pug that was bagged.

You may wonder how this could even happen so heres the story-

It was in the early 80s and I was using mostly filter pressed clay from Quyle that bidy was called sandstone buff and was th color of baby poop.

They are and still are one of the smaller family owned clay companies in the west. They are up in high altitudes in the Serria about mid state.

They filter press calyy and in the swing seasons when its not dry out they ofen left the pugs out to dry a bit in wide open bags(they had great large bags at that time. I used to drive up to the busiess and oick up small 3,000 # loads as thats all I could handle in a 3/4 ton truck. I more than once saw the bags open in the sun in the cool spring or fall air.

Well thats wher a cat must have found a bathroom -in the top of a bag. 

You can image what that was like 6 months later on your wedging table.

I now have a small pile on a shelve above the wheel with a collection of bits I have found in clay mostly wood-I may have tossed it last fall cleaning up but maybe not.

When you start using large amounts of clay you will start finding things no matter who made it.

[hitchmss]

I and a number of other local potters were finding a lot of debris in our clay from Laguna, for about a 4-6 month period, about 4 years ago. I found metal shavings, twigs/organic debris, and cigarette butts; other potters found razor blades, gravel, etc. Called Laguna who could/wouldnt offer any assistance in the matter except apologies. I assume they had a pissed off employee who was throwing stuff in the mix. I inquired why they couldnt have a metal detector at the end of their mill, to which I never got an answer.

Some stuff(gravel, twigs, etc) here and there is something I find acceptable as it would be easy enough for it to find its way into the mixer, but metal shavings and razor blades are not ok. If its a prevalent issue for you, switch suppliers.

[Benzine]

@Mark C. if you wrote a book, that was just stories about your life in the world of clay, I would buy it... And possibly even read it...

[neilestrick]

4 hours ago, hitchmss said:

 I inquired why they couldnt have a metal detector at the end of their mill, to which I never got an answer.

When I worked for A.R.T. we looked into a metal detector for the clay when a hole appeared in the stainless steel liner of our mixer and we had no idea at what point it had happened. It just wasn't feasible. It would maybe be able to find larger pieces of metal, but not shavings that would still be large enough to cut someone, and not at the speed it would need to be done to maintain a decent production schedule. So we threw out 9000 pounds of clay.

If the production crew is doing their job properly, and the equipment is maintained properly, there is very little reason for anything to ever get into the clay. I could see the occasional piece of paper bag from the raw material, but never twigs or cigarettes or plastic.

[hitchmss]

1 hour ago, neilestrick said:

It would maybe be able to find larger pieces of metal, but not shavings that would still be large enough to cut someone, and not at the speed it would need to be done to maintain a decent production schedule. Sow e threw out 9000 pounds of clay.

Good to know the answer! I know I had watched documentaries on food processing plants which had high speed metal detectors which would pick up even tiny fragments of metal, but maybe it was easier for an operation like that to afford the tech!

I say twigs, or small organics being expected/permissible; if the bags of dry clays were shuffled around the plant/yard and brushed into something, or were sat on something, I could see that slipping into the mixer (like a piece of a bag might). When I suggested that the curls of metal(needle like shapes/tubes) that I found in my clay were likely from the bearings on the auger either being worn, or out of alignment, the plant manager at Laguna couldnt or wouldnt confirm, but that's what I suspect.

[neilestrick]

1 minute ago, hitchmss said:

Good to know the answer! I know I had watched documentaries on food processing plants which had high speed metal detectors which would pick up even tiny fragments of metal, but maybe it was easier for an operation like that to afford the tech!

I think it's the difference between being picked put of a small piece of food vs being embedded in a 25lb bag of clay. Plus the cost. This, like most things, falls into the category of 'how much are you willing to pay for clay'.

[hitchmss]

Just now, neilestrick said:

This, like most things, falls into the category of 'how much are you willing to pay for clay'.

Agreed; two pieces of sharp metal in over 50 tons of clay is nothing that Id want to see my prices jump $.40/lb for.

[Mark C.]

On 2/14/2019 at 6:57 AM, Benzine said:

@Mark C. if you wrote a book, that was just stories about your life in the world of clay, I would buy it... And possibly even read it...

I will not be writing that book unless I’m bed ridden in life

the more likely book is on my life underwater,much more exciting