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Member Since 22 Aug 2010
Offline Last Active Dec 18 2014 10:26 AM

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In Topic: Spectrum Glaze Problem

17 December 2014 - 11:54 AM

This was another email I received from Jacob at Spectrum Glazes.  He sent the gum and suspender, but I haven't had time to give it a try yet.  Just thought the extra explanation may help someone else out there.



I should be clearer with this, old glazes have two materials that can be eaten by bacteria over time. They're the only organic parts of a glaze so they're the only things that can cause a glaze to "go bad" as it were, although you can always re-add them to make a glaze work again. None of the parts of the glaze that form the glass after firing are capable of going bad short of extraordinary circumstances. 

The gum is what holds it together. When it's missing you get the glaze flaking apart when it dries because the water isn't holding it together. The suspender is another part and keeps the glaze from settling out from the water. What was so strange about what you described is that only the gum is gone, the glazes haven't settled out. It's two different materials that prevent those issues, but they usually get destroyed at the same time because they're the only two things susceptible to bacteria. It's just quite rare to have only one go completely and the other not at all.


As for how to use them, I'll send both just in case, but you'll likely only need the brushing media unless the glazes start settling out. As for how to use it, take about a tablespoon of the media, it's just CMC gum already dissolved in water, and add it to the pint. Stir it in as best you can, a stick or spoon should be fine, a blender is always better, and let it sit for 15-20 minutes, then do a test, and see if the flaking happens again. If it's still happening, it should at least be dramatically less you've had so far and just add another spoonful of the media to the glaze. It's always best to go slow at first and have to add more because adding is easy, it's not so easy to take out once it's in. Adding too much gum won't be a large problem though. Too much gum will likely just make it very slow to dry and potentially thicken the glaze a bit.

If you have settling issues, the suspender will be the same process, although it's more likely a blender will be necessary, as the suspender is very thick. With the suspender I would go by the teaspoon rather than tablespoon after the first because too much suspender will be a larger problem than too much gum. Too much suspender can really make a glaze go to jelly.

In Topic: Spectrum Glaze Problem

03 October 2014 - 11:25 AM

I had some difficulty with the 900 series as well, but not nearly as much as yours show. The Old Copper in particular used to cake up and tended to flake off, especially as the jar got older. I lightly sanded pieces to try and even it out and compress the layers a bit, but towards the bottom of the jar that wasn't possible because of the flaking, even after adding some gum to the jar. I always loved the way this series looked but it was a challenge to brush on evenly and cleanly.

Nancy, the Old Copper is the glaze in the picture of the mugs that has huge curling and flaking (far left).  I have some commercial glazes that are several years old and haven't had a problem with them adhering to bisqued pieces.  I know the glazes haven't frozen while I've had them so I don't know what would have caused the gum to go.  I don't have a lot of knowledge regarding glaze chemicals, but this is the first time I've experienced this problem.

In Topic: Spectrum Glaze Problem

03 October 2014 - 11:19 AM

This is the response I received from Spectrum……I've sent the batch numbers and we'll see what happens.  
Wow, I can honestly say I haven't ever seen glazes do that, at least not to the extent they are doing it. 

I think the gum is completely gone. 

Usually, if that happens the suspenders go with it and the glaze settles out so much people never get to apply it and see it crackle like this. The only thing I can think of that would ruin the gum in the glazes and not the suspenders is maybe freezing. I'm sure there are other possibilities, but that's the only thing that I've heard of that did it that I can think of. 

Anyway, it would be helpful if you sent me the batch numbers on each pint that you have, that's the 5 digit code on the right-hand side of the label. That way I can check our batch samples and formulas to make sure they're right and that we didn't leave an ingredient out of the whole batch. I think I would've heard more by now if that was the issue, but in cases like this I always want to check.

The glaze itself could probably fire out fine as long as the cracks don't get too big. A lack of gum won't affect the fired finish if you can keep it on the piece. As it starts to melt it'll all collect and gel together, but I understand not wanting to risk that on pieces you like as if it goes wrong it'll be a crawling mess. And definitely on any vertical side the heat would likely dry and and fall before it had a chance to bond with the rest of the glaze and clay.

Send me the batch numbers and amounts you have and once I make sure it's not a formula problem on my end, which I really doubt it is, but I wouldn't want to send you replacements that do the same thing, we'll get you new replacement pints.

In Topic: Spectrum Glaze Problem

02 October 2014 - 04:31 PM

Were there other glazes in the firing that came out fine?

Have you confirmed that the kiln reached temperature? Did you use cones?

Were these the same containers of glaze from the successful tests?

Neil…..the pictures are of bisqued pieces that the glaze had been brushed on and were ready to go into a glaze firing.  


The test tiles were fired sometime ago (using the same clay and glazes from the same jars).  This was the first opportunity I've had to actually use the glazes on pieces aside from the test tiles.  After I brushed on the glazes, they all looked fine.  It was the next morning before loading the kiln that I found them in this condition.  If I touched a piece, the glaze just fell off…..but a lot of it had fallen off all by itself  :( .  


I've glazed pieces from the same bisque firing with Duncan's Artisan glazes, as well as some other glazes, and they did just fine so I can't believe it has to do with the clay or the bisque firing.  Spectrum sent an email saying they forward my email to their technical person….hopefully I'll hear from her soon and I'll post their reply.


I thought maybe someone on the forum had experienced something similar.

In Topic: Spectrum Glaze Problem

01 October 2014 - 08:09 PM

Yes Min….it was a very nasty shock!  The glaze inside the mugs is the same as the outside.  (I was using a base color on the inside and outside of the mugs, then putting a coat of another glaze - one I had already tested with the test tiles - on the outside.)  All were flaking on the inside as well as the outside although it was more severe on some than others.  I thoroughly mixed the glazes in the jars with a wire whip so I wouldn't think mixture was a problem.  And thickness could not have been the issue since only one coat flaked as well.  The consistency of the glazes were about the same….they all brushed on easily.    


I've washed all the glaze off and put the pieces in the oven to dry out.  Tomorrow I will glaze them with a different glaze.  I just can't figure this out.