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Food coloring in glazes


GEP
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I have two glazes that dry to the exact same color when applied on a pot. I’m thinking of adding food coloring to one of them, so I can see where one glaze ends and the other begins. Has anyone tried this and does it work? By “work” I mean does the food coloring burn away harmlessly without affecting the glaze? Which color is most likely to burn away harmlessly, or are they all the same? 

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I add food liquid colouring all the time to my glazes. I've never had one that didn't burn out completely. Blue seems to give the most colour for the least amount of food colouring used. If you need to flocculate plus add colour the Crayola Tempura liquid paint does both things. I recently ran out of the liquid food colouring so I used some of the paste type, that stuff is super concentrated! It does contain some organic materials but so far I haven't noticed any rot with using it. Liquid food colouring, no issues whatsoever.

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  • 1 year later...
On 6/13/2019 at 10:40 AM, GEP said:

I have two glazes that dry to the exact same color when applied on a pot. I’m thinking of adding food coloring to one of them, so I can see where one glaze ends and the other begins. Has anyone tried this and does it work? By “work” I mean does the food coloring burn away harmlessly without affecting the glaze? Which color is most likely to burn away harmlessly, or are they all the same? 

 

On 6/13/2019 at 10:50 AM, Min said:

I add food liquid colouring all the time to my glazes. I've never had one that didn't burn out completely. Blue seems to give the most colour for the least amount of food colouring used. If you need to flocculate plus add colour the Crayola Tempura liquid paint does both things. I recently ran out of the liquid food colouring so I used some of the paste type, that stuff is super concentrated! It does contain some organic materials but so far I haven't noticed any rot with using it. Liquid food colouring, no issues whatsoever.

Food Coloring in Glazes
 I add food coloring to the second "coat" of glaze to show what may have been missed; then if a 3rd coat is required a 2nd color of food coloring. The food coloring burns off in firing

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Good idea, thanks! 

Somewhat related, learned to add a drop of tempura paint to spackle, particularly when patching over white primer, as it makes finding all the spackled spots much easier after sanding smooth, for the spackle spots require spot priming if the finish is not flat. Less related, primer sticks better than caulk and spackle, so prime first, then caulk and spackle, spot prime the spackle, allow the caulk to dry fully, then let the finish flow.

So far, each glaze colour in my limited palette is unique/discernable, however, not so much the clears, hence I'm marking the bottom of the pot with code to indicate which clear, and which clay as well.

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It's been a year since I started using the paste food colouring and have had no issues with rotting / mold from the organics in it. I still am on the first jar I bought, Wilton Teal colour, for about $3, it's so much more concentrated than the liquid.  I add water to it in a small jar then pour a tiny bit into the glaze or wax resist. 

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2 hours ago, Mark C. said:

I have two iron glazes and I would like to tell them apart after dried for loading-Since they are saturated iron I am pretty sure I need something more potent ?

Blue or green may make it go purple or brown enough that it's different than the other. You could also try a black ink, but it's probably more likely to stain your skin. Or mark them with a spot of food coloring or ink after you glaze them, although that's a whole extra step.

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I may try a bottle of blue food coloring-I glaze hundreds of pots on glaze day so marking them is not going to cut it-now I separate them and its a hassle .One like cool spots the other like as much heat as i can give it. Its cheap try. I always wear gloves when glazing but ink is just not  as friendly as food color

Thanks for the ideas-now to put it on the shop list.

Edited by Mark C.
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There's no real black iron oxide, it's all "synthetic".  Or in actuality there is no such thing as synthetic iron oxide.

Synthetic red and black iron oxide are byproduct of industrial process.  They have less impurities than "natural" iron oxides but that's about it.  Natural black iron oxide is magnetite  but contains impurities, so it is "synthesized" in big pools by exposing red iron oxide to water and hydrogen(?) I think?

Anyway, would be difficult to find natural magnetite.

 

 

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26 minutes ago, Min said:

I buy the type sold as synthetic from Alpha Chemicals, they have a "natural" black iron oxide too. Particle size and impurity differences between the two. The synthetic one I get is sold as <1 micron, the "natural" is listed as 30-45 microns. 

That's funny, the natural is actually more pure on the analysis.  It has silica, magnesium and calcium, but verrrry little mg and ca.  

I've never seen natural black iron oxide outside of coarse magnetite, must be an interesting process to keep the mills clear of magnetic dust.

You'd expect the "synthetic" to be more pure, but since it's industrial waste, it has lead, cadmium, etc.

Edited by liambesaw
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Thanks for the tips about the wax--food coloring or paste-I don't often use wax on surfaces other than to rim bottoms but I used it in a textured design just today and ran into a problem  where I couldn't see the waxed areas well enough for the precision I wanted.  

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