This is way late in responding and I doubt that it is of much use but regarding the inability to get red out of the glaze "Randy's Red", when they changed talc on us our version of this glaze went from red to ugly brown. I tried any number of adjustments to make up for the change of talc and it turned out that the only solution was to add bone ash. I settled on about 2%. Most saturated RIO glazes have this in them.
Donna: I tried the slow cooling method and still ended up with the UGLY brown that is in the photos I uploaded. I spent 2 years working on iron reds and never got anything I was happy with. I may try again on my vented kiln, computer controlled...I have to have some success elsewhere before I get the courage to go at it again! LOL...
On Randy's Red - I believe the glaze originally was published in Reader's Digest Crafts and Hobbies (1981) under the name Ketchup Red. Whenever someone tweaked it at all (used a different feldspar, pumped up an ingredient by 1%, etc.) they added their name. It is very sensitive to which ingredients are used so when we had to change our talc the glaze went a flat ugly brown. I added 2% bone ash and got it back. It needs a slow cool down for the RIO to do its thing. If you are getting a pretty red inside a bowl or cup and blah on the outside then that is your problem (slow down the cooling).
I really have no idea who the Randy is! The Randy's Red has been around for quite some time. I HAVE NEVER been able to duplicate the ones that actually look like a rich brick breaking red. I spent 2 years trying!
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