Food coloring in glazes

[GEP]

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? 

[Min]

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.

[Callie Beller Diesel]

I've used both red and blue, and they burn out just fine. The blue is more visible, I find. 

[Zoie]

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

[Zoie]

Food coloring in glazes

By GEP, June 13, 2019 in Clay and Glaze Chemistry

I add one color of food coloring to the 2nd coat of glaze to see what may have been missed; a 2nd food color, f a 3rd coat is needed. The food coloring burns off in firing

[Hulk]

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.

[Min]

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. 

[Mark C.]

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 ?

[Min]

I wonder if the black paste colouring would work? I have a couple iron glazes, one is okay using yellow iron oxide in it so I subbed the red for yellow so I could see the difference.

[neilestrick]

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.

[Mark C.]

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.

[Min]

Get the paste colouring if you can, goes way further. Going forward with new batches of glaze, have you got any synthetic black iron oxide you could try in one of the recipes? Could do the math and see how much to sub for the RIO and run a test. Would avoid having two iron red slurries.

[Mark C.]

My black iron is real I think. I'll look for the paste coloring

[liambesaw]

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.

 

 

[Min]

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. 

[liambesaw]

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.

[Min]

This is magnetic too.

[Cherry]

I also use food coloring in liquid wax. Interestingly, red food coloring, which makes the wax pink, turns turquoise a few days after putting on bisque ware, but stays pink in the bottle.

Wilson paste colors.

[LeeU]

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.