Plastic clay reclaim buckets pulling iron out of clay

[Piedmont Pottery]

I routinely use plastic cat litter buckets for collecting and transporting clay slop and trimmings.  I have observed that in areas where the slip dries out along the walls the plastic is coated with red iron oxide, which also adheres to the dried clay.  This is with a white stoneware clay, not a brown or red clay.  So it appears that the trace amounts of iron in the clay are binding to polypropylene surface of the bucket. This makes sense because the surface charge of polypropylene is negative.  I typically throw the dried clay flakes that are covered with iron oxide in with brown clay waiting to be reprocessed.  Over time, my reprocessed white clay will have a lower concentration of iron, although I don’t think it will make a noticeable difference in the color of the clay,  as I don’t think it’s removing more than a few hundred milligrams of iron per batch.

[Retxy]

I too use cat litter buckets but hadnt noticed any discoloration.  Have you experimented with other buckets tonsee if this happens there too?

Ghanks for putting this on my radar

[Retxy]

But spelled right!

[Callie Beller Diesel]

Are you sure that’s iron oxide? There’s lots of other possible solubles that turn brown.

[Bill Kielb]

Tannins (fermented organics) for well water quite often assumed as Iron. Common test often included in well water test kits.

Edited March 7 by Bill Kielb

[Hulk]

I'm seeing a layer of slimy yuck against the plastic bucket, some reclaim batches, but not always - almost certainly organic growth, which goes on to its reward when growth/flourishing conditions turn "against" them...

[Piedmont Pottery]

On 3/4/2024 at 1:25 AM, Retxy said:

I too use cat litter buckets but hadnt noticed any discoloration.  Have you experimented with other buckets tonsee if this happens there too?

Ghanks for putting this on my radar

I haven't noticed this happening on other bucket types, but I have a lot of this kind of bucket, so I haven't really used many others for reclaim.  

[Piedmont Pottery]

On 3/7/2024 at 12:01 PM, Callie Beller Diesel said:

Are you sure that’s iron oxide? There’s lots of other possible solubles that turn brown.

That's a good point.  I haven't really tested to see if it's iron or something else, but it sure looks like iron.  I may try firing one of the chips of dried clay that has the material on it to see if it behaves like iron oxide. 

[Piedmont Pottery]

22 hours ago, Bill Kielb said:

Tannins (fermented organics) for well water quite often assumed as Iron. Common test often included in well water test kits.

That's a possibility, but I would expect polyphenols in water to have a net negative charge, and therefore unlikely to bind to polypropylene.

[Bill Kielb]

7 minutes ago, Piedmont Pottery said:

That's a possibility, but I would expect polyphenols in water to have a net negative charge, and therefore unlikely to bind to polypropylene.

Tannins in well water stick to most everything. Generally cause users to complain about the yellow or rust stains on fixtures (plastic and ceramic) buckets, vinyl siding or most things irrigated. Not sure what your bucket is truly made of or it’s matrix but easy to test for tannins ….. or iron for that matter if curious.

[Piedmont Pottery]

4 hours ago, Bill Kielb said:

Tannins in well water stick to most everything. Generally cause users to complain about the yellow or rust stains on fixtures (plastic and ceramic) buckets, vinyl siding or most things irrigated. Not sure what your bucket is truly made of or it’s matrix but easy to test for tannins ….. or iron for that matter if curious.

I'll fire some chips in the bisque kiln this weekend.  If it is tannins they should burn out.  This is also city water, not well water, so I expect only low levels of tannins.

[Callie Beller Diesel]

Keep us posted! Curious to know what it turns out to be. 

[Piedmont Pottery]

The material survived the bisque firing, strongly suggesting it was not organic.  It sure looks like iron oxide to me.

[Min]

I wonder what would happen to it if you scraped some into hydrochloric acid? Interesting. 

https://www.sciencephoto.com/media/859757/view/iron-iii-oxide-in-water-and-in-hydrochloric-acid#:~:text=Left%3A rusty-red solid iron,HCl -> FeCl3 %2B H2O.

[Bill Kielb]

6 hours ago, Piedmont Pottery said:

 It sure looks like iron oxide to me.

Might be! Magic kitty litter bucket replaces iron filters. Might be on to something. High iron city water or just high iron clay?

Edited March 12 by Bill Kielb

[Piedmont Pottery]

17 hours ago, Bill Kielb said:

Might be! Magic kitty litter bucket replaces iron filters. Might be on to something. High iron city water or just high iron clay?

It’s a white stoneware clay, so not super high in iron, but I suspect there’s some.  The town doesn’t report iron levels in their annual drinking water quality report, but I’ve not seen any rust staining in the toilet or sinks at the studio.

[Magnolia Mud Research]

when wondering around the property this week I notice a rotting stomp of a large pine tree that was blown down a few years ago; the dried yellow clay still on the bottom of the stomp was simular to the color of the plastic cat litter buckets;  the clay on the stump contains iron oxides.  Long ago while solving problems for plastics, fine particles of iron oxides were used to produce colors to the plastics.  

My point is you should think about the iron being taken from the plastic.  Test using a plastic bucket that is not yellow.  

LT

[Retxy]

On 3/8/2024 at 10:21 AM, Hulk said:

I'm seeing a layer of slimy yuck against the plastic bucket, some reclaim batches, but not always - almost certainly organic growth, which goes on to its reward when growth/flourishing conditions turn "against" them...

@HulkHahahaha the reward part made me laugh, thank yoh for that