[Adding plasticity to reclaim]

I like to use Veegum T to fix short batches of reclaim.  I keep a tub of hydrated Veegum next to the pugmill.  After each batch is mixed, I test for shortness, and if needed, put in a small scoop full of the hydrate Veegum and mix some more.  Veegum is expensive, but it doesn't take a lot to fix a batch of clay.

[A large 24" tall sculpture has some crazing. Is there anything I can do to save it? Sorry if this is wrong forum]

17 hours ago, Rae Reich said:

Rub ink into the crackles and say, “I meant to do that”?

I agree strongly.  India ink enhanced crazing can be very dramatic and beautiful.  If you or the gallery owner can't live with the result, the ink will burn off if you refire the piece.

[crackle glazes]

15 hours ago, s6x said:

Could a similar effect be achieved by using a color underglaze with CLEAR  crackle glaze on top?

This would probably work, but the crazing you will get with most commercial crackle glazes will be much finer than the example photos you posted.  You will need to go over the pot with India ink after firing to get dark color into the cracks.

[Wollastonite lumps revisited]

22 hours ago, High Bridge Pottery said:

Do you have a particular reason for using wollastonite? I found swapping wollastonite for whiting and silica made no difference to glazes and whiting is much nicer to work with.

Wollastonite has a much lower LOI than whiting (1.6% vs 43.9%) and has a lower thermal expansion coefficient (9.0 vs 14.8) (data from DigitalFire).  Wollastonite also provides silica in addition to calcium.   My glazes are high silica/low expansion by design, and wollastonite gets me there.  And finally, Wollastonite cost me $0.59/pound the last time I bought it, whereas whiting cost me $1.17/pound.  I'm sure I could rework my recipes to substitute whiting, but there is a certain amount of inertia involved in doing that, as I'm generally happy with the way my glazes are behaving on my clay.

[Wollastonite lumps revisited]

Some time ago I posted about challenges with wollastonite clumping.  I have now found a process which is helping with this issue.  I utilize one of these flour sifters when weighing out the wollastonite.

  I sift the material directly into a pan on the balance until I have the necessary amount.  It's pretty low tech, but it works.  Perhaps not feasible for large-scale batches, but I'm usually making 1-2kg batches of most of my glazes, and it works fine for that.

 

[Plastic clay reclaim buckets pulling iron out of clay]

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.

[Plastic clay reclaim buckets pulling iron out of clay]

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

[Plastic clay reclaim buckets pulling iron out of clay]

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.

[Plastic clay reclaim buckets pulling iron out of clay]

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.

[Plastic clay reclaim buckets pulling iron out of clay]

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. 

[Plastic clay reclaim buckets pulling iron out of clay]

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.  

[slab plates center warping during glaze fire]

For me it would be faster to just throw the plates on the wheel from the start rather than using the slab roller.   However, I do find that a foot ring adds stability to plates during firing.  Have you considered using a slump mold instead of throwing the slabs?

[Moving a Duncan DK 1029-1 and bringing it back to life]

If the controls are corroded you may want to look at an external computer controller.  That is what I did on my old Duncan 1029.  It will cost more up front but will really help with more consistent firings.  You will have to drill a small hole for a thermocouple to go through.  all the infinite switches are set to Hi, or bypassed altogether.  I did leave the kiln sitter inline to have a failsafe option. 

[Peter Pugger works only sporadically]

I haven't had that problem with mine, but I've found Peter Pugger technical support to be very friendly and helpful when I've called about other issues.  They should be able to offer suggestions.

[Building a Genesis Log File Grapher website for me and community - need feedback!]

Will your program accept multiple log files for long firing time programs?  I often have two, sometimes three log files per firing, depending on the program.  Also, I'm hoping that your program will be compatible with first generation Genesis log files.  I'm really looking forward to your finished product.

[Heating /cooling source in pottery studio]

I installed 2 mini splits in my kiln room and they work well.

[Crawling of clear glaze over underglaze]

Are you bisque firing after the underglaze and before the transparent, or are you single firing?  If you are bisque firing first, how well adhered does the underglaze appear to be before applying the transparent glaze?

[Clear glaze that does not craze on MB]

57 minutes ago, Christy Ann said:

I have the cone 6 clear formula our studio is using with MN Clay MB. It is for Shiney Clear:

wallastonite 2250 grams

frit 3195. 2250 grams

epk 1500 grams

flint 1500 grams

if you are able to help us revise the recipe or find a new recipe that works with this clay I would be extremely grateful!

 

This is interesting, in that the calculated COE is low enough that I wouldn't expect it to  craze  on any of the clays I use.  Regardless, my usual fix for glazes with too high an expansion coefficient is to add a bit of talc.  I'd begin with maybe 250 g talc added to the amounts you listed as a starting point and go up from there.

[Proper Pugging]

36 minutes ago, Min said:

Veegum T does make clay lovely and plastic doesn’t it. Now if only it wasn’t so expensive! 

But it only takes a little bit to fix a batch of short clay, so not too bad overall.

[Proper Pugging]

Veegum T is the magic additive I use when a batch is too short.  I keep a container of hydrated Veegum T next to the pugmill so I can just add a small scoop to the pugmill if I need too.  I am also very diligent in recovering as much of the fines as possible when reclaiming.

[Carbonato de bario]

I substitute strontium carbonate for barium carbonate, 0.75 grams strontium carbonate per gram of barium carbonate in the original recipe.  You will probably have to adjust this a bit, and you will see some shifts in color of the glaze.  Strontium is non-toxic, as opposed to barium.

[Toxicity transfer in alternated firings]

This definitely happens with lead glazes.  Lead is very volatile at glaze temperatures and will bind to the kiln brick, and then a portion of it will re-volatilize on subsequent firings and will bind to everything in the kiln.  For other potentially toxic metals the extent to which this can happen is dependent on the volatility of the metal at firing temperature.

[Plastic clay reclaim buckets pulling iron out of clay]

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.

[irregular cracks on fired cone 10 pots]

Delayed cracks can be indicative of a glaze with a thermal COE lower than the clay body.  You might try to increase your glaze COE a bit to see if the cracks still happen.

[Used old shelf primer and this happened, can you help?]

It looks to me like you had enough organic materials in the kiln wash to create a reducing environment in the kiln and you got a lot of carbon going into the surface of everything.  If that is correct, refiring with plenty of air available, e.g., peeps open or lid propped open just a bit, should burn off the trapped carbon.  Fire it up to your normal working temperature.