Numerous members have used SCM and Jen's Juicy Fruit with excellent results. I believe the crystals being objected to are some kind of crystal that is growing in the melt upon cooling, not unmelted strontium poking out of the matrix. The crystals have sharp diamond reflective points which would not be present if they had been even slightly attacked by the glaze fluxes, of which there are plenty, evidenced by the fact that the glaze is very prone to running.

My understanding is that Catherine Rehbein uses commercial glazes, not SCM,

I had the same kind of crystals form in pots fired to cone 9 both reduction and oxidation at the a Steven Hill workshop in 2009.

You can render your rough pots smooth as a baby's bottom with about ten minutes of sanding with 200 and then 400 grit carborundum wet sandpaper, but the sparkly effect will be gone. 

Comments that were previously on the group Comment Wall rather than a threaded discussion:

Comment by Norm Stuart 13 hours ago

I would definitely would like to know what Cone is required to make Strontium Crystal Magic fire like Cathy Rehbein's work. I know from experience it's obviously much hotter than Cone 6 - the same with Jen's Juicy Fruit which is a non-event at Cone 6 oxidation.

Especially given the fact that this is at least nominally a Cone 6 website.

I found kitchen white vinegar easily bubbles off the CO2 from strontium carbonate, making it into strontium acetate which decomposes into Strontium Oxide at 459 F, much lower than Strontium Carbonate - although no one agrees on what that temperature is exactly.

I'm going to try this lower melting strontium in some glazes to see if they look different than the one which use strontium carbonate. The drawback is 43 grams of strontium acetate dissolve in a liter of water, so that will produce a different result as well. I different result I suspect may be quite useful based on the ceramic makers who put strontium frit into their clay bodies.

I've spent a lot of time reworking alleged Cone 6 glazes so they actually fire well at Cone 6. Pete Pinnells Weathered Bronze Green was one of them. Pete says it was originally a Cone 10 glaze and one of his students found it also "worked" at Cone 6. I found "worked" was too subjective and likely the result of an inaccurate kiln temperature which had to have been hotter than the student thought.

Making Weathered Bronze Green into a true Cone 6 glaze required the addition of 20% Ferro Frit 3269. After that addition it looks as beautiful as when it's fired to Cone 10. It only stands to reason it couldn't possibly look the same after firing to Cone 6 without a change in the recipe.

Comment by Norm Stuart 22 hours ago

Robert - In my experience Strontium Carbonate doesn't incorporate well into glazes at Cone 6.

There are special Strontium Frits available,  especially used for glazes at Cone 2 and below, but these are quite costly.

I'm actually headed to the studio right now to try vinegar and HCl on strontium carbonate. As for migrating into the bisque, that has benefits as well. Just add more strontium chloride.

Comment by Joseph Fireborn 22 hours ago

I am new to this stuff haven't done chemistry in 15 years. I did add the vinegar to the strontium carbonate and it immediately foamed up and had a reaction like you stated. I did wear a safety mask. I will probably mix up the batch of scm with the acetate tonight and spray it in a few days.
Comment by Robert Coyle 23 hours ago

I'm not sure what people are looking for here. both Strontium acetate or chloride are bot very soluble in water, so they should be absorbed into the clay body and leave not much in the glaze.

Comment by Norm Stuart 23 hours ago

Acids combine with stronitum carbonate to bubble off the carbon dioxide (the carbonate). What you end up with depends on the type of acid used.

Vinegar (acetic acid) creates strontium acetate.  Nitric acid would create strontium nitrate, sulfuric acid strontium sulfate etc.

If Vinegar is strong enough to get the reaction with strontium carbonate going you'll immediately see foaming as you add the vinegar to the strontium carbonate and the carbon dioxide and water vapor bubble off. It should look just it does when you add vinegar to baking soda.

If vinegar is not strong enough to start the chemical reaction on its own, you'll need to heat the mixture over a stove, use a stronger concentration of acetic acid, or more realistically use a stronger acid like hydrochloric acid (called Muriatic Acid at a pool supply store) packing enough energy to break off the CO3 as CO2 and water vapor.

As it sounds like you're new to chemical reactions, always add a strong acid or strong base to the chemical to be added. Never add the chemical to be reacted, in this case strontium nitrate to the strong acid or strong base. This could generate too much heat in that localized area causing the acid or base to boil and splash back at you. Always wear safety glass or goggles. I just picked up 8 of them from Amazon for $2 each for studio members using our new glass saw and glass grinder.

Stuff is real cheap on Amazon as they've recently relaxed the requirements for direct ship from China. Rather than buy a Bohl glass circle cutter for $85 I purchased a nearly identical Chinese version for $5.90, which included the shipping cost from Shenzhen?! Shenzhen is on the border with Hong Kong and is the official exit point for most goods produced through-out China, on their way to the rest of the world.

 From memory I think Catherine Rehbein fires her SCM to cone 8, but you'd have to confirm this with her.

Comment by Joseph Fireborn yesterday

So soaking strontium carbonate doesn't sound that hard. Do you think it would fully absorb into the vinegar? Or do you think if I evaporated the vinegar it will return to a type of powder?

I guess I will have to test and see. Im thinking I will mix a 2 test batchs of SCM, and a control batch. I will put the stront carb into the vinegar and let it soak overnight. I will then just directly pour one into the glaze mixture and then adjust flocculation with darvans. Then I will take another vinegar batch and try to dry it out and see what happens. If I can dry it out I will run another test using that SCM batch, and I will run a control batch just to compare. I will run the test using currie grid to see if there are some interesting results that I might be missing. 

It will be a few days before I can run the grid test, I grid tiles drying right now, but how long do you think I should soak the SCM? 24 hours 36 hours? 48 hours?

I have a friend who does a lot of experimental stuff with glazes I will contact him and see if he has any opinion. 

Catherine Rehbein's work is really nice and colorful, and your right it is glossy and not a sandy matte look like SH's work.

Comment by Norm Stuart yesterday

Catherine Rehbein fires a lot of clearly glossy melted strontium crystal magic pieces, so I'd be very curious what firing she uses to achieve this.

Strontium oxide produces brilliant colors like lead with low thermal expansion and can be a flux above Cone 2.  But Strontium Carbonate doesn't decompose until an astounding 2,721 F, a good 350 F hotter than Cone 12.

If you're interested in an experiment, before adding the strontium carbonate to the glaze, I'd first react it with an acid like vinegar or hydrochloric acid to release the carbon dioxide.

Strontium acetate and strontium chloride both decompose below Cone 010, but at the expense of being far more soluble than strontium carbonate. I'm curious if this would make any change in the firing behavior of SCM.  It seems unlikely but potential surprises lie in wait out there.

Comment by Joseph Fireborn yesterday

So you think I should try getting closer to cone 7? I can do a hold at cone 6 and hold for like 30mins or something and see what happens.

Comment by Norm Stuart yesterday

My impression has been SCM requires more than a Cone 6 to achieve the results I see others showing. The same too with Jen's Juicy Fruit. For me at Cone 6 both have too much unmelted materials - particularly the strontium in SCM.

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