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I am using the Riggs process in one step naked Raku with cone 08 bisque Phoenix clay body with terra sigillata surface. The pop off slip includes Hawthorne fire clay. I am having issues with most of the slip falling off during the firing. I have increased the Alumina Hydrate by 300 grams with little improvement (started with 700 grams in formula). Have thinned the slip with water and firing to to 1450 F.  Not sure what other variables to consider to get the slip to stick better through the firing. Any suggestions? 

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From the article linked below from Charlie and Linda Riggs, they put the pot within minutes of applying the slip into the kiln and not to allow the slip to dry at all. Is this the way you are doing it also? I wonder if adding  gum to the slip would help? 


(behind a paywall but can access 3 free articles a month)

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Thanks for the reply! I do run the pot out to the kiln wet and heat up fast to 500F then let it soak for about 10 minutes till dry and then heat up to 1450F. The slip starts popping off even at 500F. Thought the added Al  Hydrate (300g) would help, but can see no difference. Guess I’ll add more another 100 g.
I did see that the Riggs found another fire clay, Lincoln, that held better to the pot. That’s next! 

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Pure speculation ...

If you continue having problems -- I wonder if the t-sig might be the issue, for example

- by not adhering to the resist slip sufficiently
- by not adhering to the body sufficiently (any signs of  t-sig on the AWOL slip?)

Obviously it works well for the Riggs, as can be seen in
Terra Sigillata 101: How to Make, Apply, and Troubleshoot Terra Sig
Naked Raku Orb by Charles and Linda Riggs, 2003. 7 in. (18 cm) in width. Stoneware painted with white terra sigillata and polished with a soft cloth, bisque fired to cone 010, covered in resist slip and glaze. Sgraffito through glaze before raku firing to 1400ºF (760°C).

... but do any of the t-sig troubleshooting ideas in the article apply?

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Thanks for the link Peter. I have that info, but did notice that the bisque firing temp for the pot photo was cone 010. I bisque to cone 08. Maybe that lower temperature difference allows more tooth for the slip to adhere. The additional 400 grams of Alumina Hydrate to the 5 gallon bucket mix is not helping slip adhesion. 700 grams was the formula recommended amount. I added 100 grams at a time for each new firing. 

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