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I could see mullite tubes to suspend the elements from a frame work in the corners of the kiln with fiber like this would work.

It's used as a ceramic canvas for drawings which is then fired. Robin Hopper demo in the video below.

@tinypieces, video below showing how to's and why's of a damp box. (includes how to mix up the plaster) Wow, and here I thought my wax was expensive! If misting works over underglaze then wonderful, my underglazes (mostly Spectrum) have enough binder in them that misting doesn't soak into the clay very well though.

I can see if there is too much WD40 it could cause problems since it's a water displacement product. I know if I use too much WD40 on molds my porcelain cracks like crazy.

They shouldn't explode Lee. Terracotta is porous so it's easy for any moisture to escape. I'ld put a test piece or even some shards of the same type of pot in a saucer and fire it up to ^04 and see what happens. If the pots are Mexican terracotta they could be made from a really lowfire clay.

What Mark said then put them through a sieve, 80 mesh would be fine. If anything is left in the sieve then add a little water to it and microwave it until hot then put it through the sieve. To get the sediment out of the bottom of the container pour off all the liquid you can then use a loop trimming tool to cut the sediment out. Are these dipping glazes or commercial brushing glazes? Welcome to the forum.

If you don't finish the piece in one session I would use a damp box. (it's just a plastic bin or tote with a tight fitting lid that you pour plaster into. Once the plaster has cured you place your piece(s) in the box and the damp plaster keeps the pot from drying out.) Don't use the plaster too wet or you can get water splitting of the pots. (been there done that) Re the Forbes wax, it's going to depend on how thick and how dry the pieces get while you are working on them. It's not going to hurt to do both inside and out with it, yes it will completely burn off during the bisque. It's expensive for me to order in Forbes, I don't know if it is for you too? You could use Forbes on the underglazed part and a less expensive wax on the non-underglazed part to save some money.

Wax resist will slow down the drying. I like Forbes wax, the oil based ones I find don't dry as well and can be a bit gummy or sticky unless they are left to dry for a fair while which defeats the purpose. I use a size small 3M respirator and find it fits me well.

https://duncanpaintstore.com/og803-mother-of-pearl

@Olinda, are you looking to have the iron colour on a glazed piece or is it for non functional but you want a bit of shine to the iron? If you're looking for something to add to the iron for a non glazed finish you can mix iron oxide with gerstley borate. I've used it up to cone 6 as 50 red iron oxide plus 50 gerstley borate. There is shine to it at this ratio. If you want it less shiny then decrease the gerstley borate, try it with 50 iron and 10 / 20 / 30 gerstley. (don't use the 50:50 version on the bottom of a pot, it's fluxed enough to stick to the kiln shelf)

For anybody looking for a good intro to glazes the terrific book Mastering Cone 6 Glazes by John Hesselberth and Ron Roy is back in print, including colour pages. If you are interested in ceramic glazes, slow cooling, durability and host of other subjects this is a great book to own. Price is reasonable. from Amazon from Echo Point Books and Media (the publishers) from Barnes & Noble

Can you order some in from India? I did a quick Google search, Ravi's manufactures frits, including some boron ones. You could contact them and ask who the distributors are in your area. Also found that Bhoomi Pottery has Gerstley Borate. If you are going to be working at cone 6 I really do think that it would be worth finding a source of boron. A zinc fluxed Bristol glaze is one possibility of avoiding boron but having boron available will open up many more glaze choices.

I'm not seeing anything that contains boron. Is a boron frit, gerstley borate or even ulexite available to you? Boron isn't necessary for high fire but it's really beneficial to get a good melt at cone 6.

@Stone Fig, glass does look gorgeous when fired on clay but there are definite safety concerns with this practice. You mentioned you were looking for a glaze to fire on the inside of a bowl, I'ld really reconsider firing glass on a functional piece. There is a very strong likelihood of getting glaze slivers coming off the melted glass, might not happen straight away but it's a distinct possibility that it will happen sooner or later. This subject has come up several times on the forum, can do a search for other opinions on it, one link below that I started that discusses it.

I buy a drink from the nearest coffee shop and save the cup. When I need to use the washroom I take the cup with me and use the one in the coffee shop. Sometimes they say they are for customers only so I just wave the cup at them when I go in. Those porta potties can get really nasty at a busy market, probably worse for women than men.