Inlay/Mishima slip shrinking!

[rannedom]

Hi! I’m experimenting with inlay/Mishima for the first time and running into a problem I don’t understand. When I add the slip or underglaze to the carved area, I am careful to fill it up a little over the carving to allow for evaporation as it dries, but most of the time it dries dramatically—leaving huge gaps behind within the carved area.

I have tried carving through wax (preferred) vs carving  directly into the clay, making deep cuts vs shallow cuts, using thick slips/UG vs thinner slips/UG, larger vs smaller tips on the slip trailer, filling it exactly to the surface vs exceeding the surface, slow dry vs quick dry—every variation I can think of so far, and I have about a 10% success rate of getting the slip to surface level on the first try. I’ve come back two, three, four + times and it does the same thing. Some eventually start fill to the surface, but where on earth is it going? 
I generally have a good understanding of how clay and glazes and UG fit and shrink and interact, but I simply do not understand the mechanics and technique here. 

I’ve looked at tutorials and the slip/UG seems to go on easily, none of this shrinking and cracking. The finished pieces come out with a smooth surface, not contracted under the surface. I’m so excited about the possibilities here but need insight on what I might be doing wrong. 

Attached pic is waxed ochre ^6 from NM Clay carved with Diamond core FP tools and filled with amaco underglazes, at least 4 attempts to complete the inlay (meaning I repeatedly used a slip trailer to fill it to or just above the surface). The only one that has finally reached the surface is the blue, which was the thickest going on, but it still took 4+ tries. The purple line is so thin and shallow I thought for sure it would fill by now, but no. 

Any ideas on what I am doing wrong?

thank you! 

 

[Russ]

My guess is that the slip or underglaze contains a fair amount of cmc gum, bentonite  or other "brushing medium" which makes them to flow or brush easier BUT they act as a thickening gel and therefore capture and retain a large amount of water.... you put it on and the water soaks in leaving only the ug or slip behind. The water content in there might be 50% or more leaving you to have to fill several times.  You could try to make your own slip or ug without the gel producing chemical. There are plenty of recipes out there and you could the adjust them to your preference.

Edited January 11, 2023 by Russ

[Callie Beller Diesel]

Most of the folks I’ve seen do any kind of Mishima technique usually trim the surface of their pots. I’m thinking of MIchael Klein’s IG videos where he’s scraping white Mishima slip off of the pot’s surface to reveal the patterns below. I’ve also got a Katy Djreiber wax Mishima mug that feels like the surface was probably scraped with a metal rib or other trimming tool, or maybe even wet sanded after the bisque. 

So it might not be that the shrinkage of your clay and UG or slip need to be matched perfectly, it could be that the extra scraping/compressing levelling step is key to getting the surface flush. 

 

 

 

[Pres]

I did Mishima years ago, using a medium brown colored clay, and a white clay that both had the same percentage shrinkage.  I did my carving in plates on the dark colored clay and then used a pasty slip to cover the area. I applied this slip with rubber ribs, smoothing it into the plate. When drier scraped the surface with a metal rib to expose the brown clay and the decoration. Never had a problem with decoration shrinking away from base pot. In the end, I decided the technique was not the look I was after and took longer than my attention span would allow.

 

 

best,

Pres

[rannedom]

Thank you for the input! I’ll look into the brushing medium issue and also consider designs that could do well with scraping. Really appreciate it

[Babs]

Underglaze whilst containing clay may contain other stuff. Slip is clay usually to avoid what Russ is writing about, it is mixedvwith minimum water and lhquified by adding a defloc. Darvan or sodium silicate. It is plastered on when pot is leatherhard, spritz the pot beforehand, and scrape the excess off when dried enough not to smear.

You can stain the white slip with stains, prob a cheaper way to go anyway. 

Not sur wht look you are goung for or what glaze you are putting on top but maybe if hooked on slip trailing, onglaze decor. The way to go?

If underglaze can be applied with slip trailer, too  "liquid " unless pepared, as Russ states, go for "thixotrophic" searches.