Min

Could go faster to 1500F then resume your regular schedule. edit: I just read your other post about this in the another section, given they are very important pieces the safest bet would be to do the same schedule but without any candling (if you did this). Maybe go a bit faster but not breakneck speed. I'm going to delete your duplicate post.

This thread is a continuation of this one started by @Mark C. regarding the addition of another K2O feldspar to replace Custer: Vardhman feldspar from India. Chart comparing Vardhman with other potassium feldspars plus the analysis I received from Vardhman.

I have the analysis for Vardhman, I'll add a pinned thread on potash feldspar changes. edit: Pin link added here. https://community.ceramicartsdaily.org/topic/41698-potash-feldspar-comparisons-of-custer-mahavir-g200eu-and-vardhman/

Good find Peter. When I look at the analysis for both there are other differences too though. Definitely a fragile mechanism to get the green. Reitz Green with Gillespie doesn't need the lithium carb and dolomite additions when I played around with altering the recipe, the silica is a tiny bit higher in the Gillespie version but given the differences in the Floating Blue recipe that might or might not be consequential, I don't know. A simple addition of iron with a reduction of cobalt would be simple to test Hansen's theory if it translates to Reitz Green also. I suppose RIO would be the logical material to add as long as speckles don't become an issue. Or black iron oxide might be better if you have it.

I would. 1550F is approx cone 012 so pots are going to soak up glaze much faster than a typical 06-04 bisque.

@oldlady emailed me photos but was unable to post them here. These are her photos and show where she has reglazed some areas.

Is this the original you were using? I've also seen this with 1 rutile.

What have you supplied the boron with so far? Same really high alumina? Same batch of rutile?

It might just be as simple as thinning down the underglaze with water and applying 2-3 coats to get the opacity of colour you are looking for. If underglaze is applied too thick it can definitely lift from the clay. What works for me is putting the first coat on fairly thin then when that layer is dry I apply another 2 coats to get an opaque coverage. I mostly use Spectrum underglazes but have also used Crysanthos, Velvets, Speedball, LUGs and homemade underglazes. The only time I don't water an underglaze down is when doing an underglaze transfer.

Is it just the tiny bit of GB you are replacing?

Hi Steph and welcome to the forum. Linda Arbuckle pdf with a good recipe on page 4. What is helpful from this pdf also is the troubleshooting tips on page 3. https://www.lindaarbuckle.com/handouts/slips-and-engobes.pdf Which brands and colours are burning off?

If the SG was 1.36 to start with but seems thinner now it's probably just because some of the solubles in the glaze deflocculating it.

If the bottoms are a bit warped and you want to level them out you can use a diamond flat lap disc to do that. I stick one onto my wheelhead just by using a (knockoff) Xiem BatMate and water, could also use a pad or donut of clay. I dribble water onto it while the wheel is going at near full speed. It can take a few minutes to grind the bottom level but it works, makes the bottom really smooth too. I have 2 flat lap discs, one is 80 grit the other 100. The 100 grit is a better quality (more expensive) one and works better. I can post them here for you if you can email them to me. I'ld be super cautious refiring ware that has been used. Unless it's completely dried of all moisture it can give some really bad blowups in the kiln, especially if it's quite a tight body with low absorption, makes it harder for the moisture to escape.

Just to clarify the options are to spray on some more glaze and refire to cone 5 or cone 6? Risks are applying too much glaze? I don't know how that clear fires at cone 5. It would probably be okay but I'm not certain of this. Perhaps placing it in a cool spot in your kiln and do your usual cone 6? Glad that high calcium clear is working well for you!

I rarely need to level the base of a pot, if the pot has a foot ring (most om mine do) I don't try and level the entire base. I trim as usual then when I have the foot ring trimmed to width I trim a bevel into both the inside and outside of it then just use a loop tool to cut off the tip of it. Since it's just a very small amount of clay getting cut off it's easy to hold the tool level to do this.

This would be a better choice, you can always wedge in some chamotte/grog.

Do you know what the specific gravity of the glaze is that you did the one dip of? How long did you did it for? Have you tried a much thinner coat of the same glaze? Amaco does publish a colour chart with all their Velvet underglazes fired to 05, 5 and cone 10. If you scroll down to the blacks it looks like both the Jet and Velour Blacks survived cone 10. From the little inset blurb about clay and glazes used it appears that HF9 was used on both the cone 5 and cone 10 samples. If you try this commercial glaze please do check with Amaco on this as this is actually a cone 5 glaze. https://cdn.shopify.com/s/files/1/1023/7667/files/Velvets_Underglaze_all_temps_brochure.pdf

Nothing to do with the make of the kiln but I would suggest taking those shelves and posts off the lid of the kiln. Lids are expensive to replace if they crack.

Hi Helena and welcome to the forum. Is what you are making functional ware or nonfunctional? What is the maturing cone for the clay you are using? Is this a commercial claybody and if so could you post a link to it? Could you post a picture or two showing the shivering?

Or mica perhaps?

Everything makes a difference with Shino glazes so yes I would expect something different from the last time you used it. Anything else changed? Claybody, how long you let the pots sit before firing, firing schedule, how you comb you hair etc.

Hi and welcome to the forum. Just to clarify you are slurry mixing the slaked dry clay and including throwing water? If this is the case then adding some more plastic materials can fix this but I would test the reclaimed batch for absorption in case it also needs a top up of flux. For slurry mixing adding a 2-3 percent of bentonite (by dry weight) will get it back to being plastic. Easiest way to get the bentonite to mix with the clay slurry is to put the dry bentonite into a container of super hot tap water then whiz it up with a hand/stick blender for 10 minutes of so. It will turn into a very thick sludge, add enough water to make it like yogurt consistancy then add it to your clay slurry and use a drill with a jiffy mixer attachment (or similar) and whiz everything together. Tony Hansen from Digitalfire recommends dry mixing the bentonite with ball clay at a 1:1 ratio and using that. I haven't done this so can't comment on how well it works but basically doing the same thing. If you already have a batch of processed reclaim then try wedging in about 20% new clay, this might be enough to bring it back to a workable condition. BTW it is common to use nepheline syenite as a body flux.

Do you ever use roof flashing for casting of simple one piece molds? (just curious)

Hi Henry and welcome to the forum. Since you are in the countryside then zoning/regulations for a gas kiln might not be a problem but it's something I would look into, also if you have home insurance I would look into that aspect also. Do you have someone or somewhere that could walk you through firing with gas?

Hi and welcome to the forum. There is a thread linked below discussing iron speckles and granular manganese that should be of help. There are some images of both iron and manganese speckles. https://community.ceramicartsdaily.org/topic/26989-how-to-add-speckles-to-a-claybody/