Customer comes into my tent and sees my lazy susan set. It was a lazy susan with a sign on it saying "Lazy Susan" so people knew it wasn't just a platter. She very loudly said "Well, how do you think that would make Susan feel?" She was super indignant and stomped away in a huff.
I've told this one before but it's still my favourite goofy customer comment.
Don't beat yourself up over this, you learned something and in the grand scheme of things thats what counts. There are a gazillion horrible glaze recipes out there, some will say they are not food safe but most won't.
Actually, I would suggest a couple changes to your list.
Gerstley Borate can be subbed with 3134 most of the time with glaze calc program. If you post the recipe using it here someone could rework it for you. I still use Gerstley Borate in some recipes but you can probably get away without it and some of the problems it causes. On the other hand it's cheap so no biggie if you pick some up and try it.
Lithium Carb can only be subbed with spodumene but again you need to change the recipe to fit it in. I would go with the lithium carb as you will only need a few percentages at the most in a glaze.
Silica, 200 mesh is fine for most glazes. Some glazes call for 325 mesh to help reduce crazing.
For iron oxide and rutile there can be a great difference in quality from different suppliers. I order all my colouring oxides from US Pigments. For the iron the high purity red one and for rutile the light one.
Alumina hydrate, for making kiln wash.
Not sure what eps is? Typo for epk? Yup to that.
There has been a bit of confusion with the replacement for the old G200, I would talk to your supplier and see what they are carrying in your part of the world.
Ball clay, I'm on the other side of the continent from you so I don't know what's available for you. Again, I would go with what the local place recommends.
I would also pick up some Minspar and dolomite and or talc.
For kiln posts I would suggest getting more of the height of the pots that you make the most of. You will need 3 of the 1/2" ones to raise your bottom shelf off the floor with. You will likely need the bottom and probably top shelf to have a wider space between shelves than the middle of the kiln, unless you have a 3 zone controller. So, taller posts needed for the second shelf up and and one at the top. I use broken bits of kiln shelves for adding a titch more height so would probably get more of the 1/2" ones. You need to have 1 element between shelves at a minimum so no point in getting a lot of short posts unless you are using them to increase the height of other posts.
For bisque firing I would just get the 04 cones if you have to buy them by the full box. If you can buy single ones then I would get a few of the 05 and 07 and use those just until you are comfortable with your bisque firing. It doesn't need to be as exact as the glaze firing. If you are firing ^6 then I would get 5,6 and 7 but skip the 4.
I wear nitrile gloves when handling glaze materials. If you don't have one already then a definite must is a well fitting respirator/mask with a P100 rating.
Not sure if I understood your questions, but if you are asking about bentonite, yes, I would get some of the white firing kind (or macaloid or veegum) if you are planning on doing clear/transparent glazes, you don't need a lot, 1/4 lb would be plenty for now. I would also get a tiny amount of epsom salts, this might be cheaper at a drugstore. If your glaze is low on clay the bentonite will help it play better. I don't use deflocs as often as flocs, would probably skip the deflocs for now.
As for glaze thickness when Britt talks about the thickness of a dime he is talking about after the glaze is dipped and dried on the bisque. Easy way to see thickness is to take an unfired glazed test tile and scratch through it. Do 2 tiles and keep one unfired for reference. When you do your tiles do 3 different thicknesses, 1 dip over entire tile, then when the sheen is off the glaze redip it about 1/2 way down the tile then do a third dip on one upper corner of the tile. (I like using tall narrow tiles, leaving a wide unglazed strip to allow for runs at the bottom of vertical tiles)
For bisque firing just fire to whatever you usually would, probably 05 - 04 and stick to that for future loads so each load of bisque is about the same porosity. So for your first round of tests I would do the 7 glazes without underglazes or stains plus the 7 glazes on another set of test tiles with the underglazes or stains. (some stains have an effect on glaze melt)
If a glaze looks okay on a test tile and it's for functional pots I craze test it (320 oven then plunged in cold water X 3 cycles then rub sumi / India ink on it to see if its crazed). If it passes my craze test then I use it on a mini pot to see what it really looks like. Seems a glaze can look great on a test tile only to look meh on a real pot. Getting a well fitting clear sounds easy but I've found it one of the harder things to do.
I would also suggest starting a code of some sort that works for you to mark your tiles with and keep good records.
Came across this site on Etsy for laser carved rolling pins. The larger ones are approx 2 1/2" diameter X 10" rolling surface. Nice to see some alternatives to the ones at potters supply stores. (there are 3 pages of designs, sets of small rollers plus the larger ones)
If you think its from firing and not a cooling crack then slow down the temp rise during the inversion zones. (I would also slow it down when cooling through these temps as platters like to dunt when refired) So slow down the firing starting at about 1000F up to about 1100F and to be safe you could slow it down from 400F to 500F also.
My guess would be from moisture getting into the clay through repeated dishwasher, hand washing and just plain usage. The accumulated moisture is getting hot as it's heated in the microwave. You could do an absorption test on the clay to see how porous it is. What clay are you using and do you know for sure it was fired to ^6?
am i the only person who thinks that video is one of the worst i have ever watched? the technique was a poor way of doing anything, the slip was not colored so why use it at all and the scraping of clay in a room full of people breathing the stuff in was the dumbest safety violation i remember anywhere. is it just me?
The lady in the background with the double jointed elbows was kinda interesting.
Thought I would share what I have found to work for marking test tiles easily and cheaply. The Dixon (Hi-Heat) China Marker pencil in brown lasts through ^7 oxidation firings on my test tiles. It stays clear and legible and is way cheaper than the ceramic underglaze pencils. ($7- for a dozen china pencils on Amazon versus around $12 for one ug pencil) It's kind of waxy so doesn't smear or rub off if you wipe glaze drips off bottom of test tiles. It doesn't leave any ghost marks on the kiln shelves.
It does burn out with glaze overtop but for test tiles it's brilliant. Haven't fired it hotter than ^7 so don't know if it will do ^10 but I think it would.
I plunked the recipe into Insight and played around with increasing and decreasing the ingredients just in case you made an error in the weighing out like you mentioned was the possibility. If you had put only 10 silica in and 30 spodumene then the Si:Al ratio goes from 8.57 to 6.38 which along with the slow cool could be enough to make a matte glaze. Also, if the error was with the OM4 ball clay the the Si:Al ratio is 6.37 ( 10 silica, 30 ball)
Does it feel like an alumina matte, or a silky / buttery matte?
I would include a test tile with no colour additives as a baseline.
Also, do you need to slow cool if you are going for a gloss?
I think there are potter's pots and potters' glazes and pots fort he general public.
I use my potters' pots and buy potters'pots but my best sellers are not to my taste.
I do "like" them at the level of, well they work and are well made, just do not feed my soul.
Schitzo here .
This is the thought I have every time I use a blue glaze or slip. Blue sells, I need to sell pots therefore I make pots with blue. I don't have a single blue pot for our use in the house.
I would much prefer to make carbon trap shino glazed ware, wood or soda fired but it also comes down to what firing methods are available to me. Living in the burbs I don't have the option of firing a gas kiln let alone a woodfired one.