Can I add oxides to my slip? Iron oxide & cobalt carbonate in my clay body
Вставка
- Опубліковано 29 бер 2022
- There are lots of recipes out there for glaze. But far fewer for getting colored clay. The most common practice (which I've done myself) is to add mason stains. These provide a nice stable color, but are not the cheapest. I wanted to see if adding oxides used for coloring glazes could also be used in my slip. The answer is yes! I test 4 different ratios of iron oxide to cobalt carbonate: 0 parts cobalt carbonate to 10 parts iron oxide - so just iron, as well as 1:9, 2:8 and 3:7 parts cobalt carbonate and iron oxide respectively. I did all of these at a level of 4% by dry weight of the clay in my slip. The results turned out well and now I want to test even more!
Etsy Shop: www.etsy.com/shop/potterybydr... - Навчання та стиль
So helpful! Thank you for the video, it was really helpful to see the process and the final result. :)
That's great the hear!
Hi Kent! You're a magician! I was just wondering about this topic. And I totally love the cloudy white effect of your glaze! :)
Your slip casting videos are very valuable - I'm learning a lot and going to try out slip casting myself.
THANK YOU.
Hi Kitija. You are welcome and thanks so much! I'm very much learning myself. Have fun with slip casting!
Nice video, very informative. Thank you!
Glad you enjoyed it!
Omg!!! Big thx for this video!!!!
No problem!!
I like the 2:8 black slip the best. Nice work!
Thanks for the feedback!
The cobalt is so strong! I would love to see a follow-up experiment with varied iron oxide, love the honey colour but I read it can be red/brown too. Thanks for sharing.
Awesome 👌
Thanks!
Nice work, Kent! I also really like the #1 tile, for a speckled clay body. I am excited to see how the other tiles turned out. I did wonder, why didn't you do the opposite extreme of 10:0. Did you already know what would happen?
Yes just the iron oxide was a pleasant surprise. I'm guessing the speckled effect is from not using a sieve so it left some clumps. But I'll take it!
As far as higher ratios of cobalt carbonate, everything I saw for glaze recipes was lopsided like this. So I do not know what will happen on that end (like 10:0). My guess is it would be blueish. It also seems rather potent, so a lower overall percentage might be the way to go if just using it.
Thanks Kent, that was such an informative video. I love the speckle clay, not as keen on the darker test tiles but maybe for the right project the darker colors would be suitable. I wish I knew your clear recipe but I completely understand why you wouldn’t want to share that, LOL. 😉
The recipe for that glaze is trivial and happy to share - it's clay planet's cone 6 base glaze and water. What they make that glaze from - I have no idea!
@@PotterybyKent Thank you!
Awesome video. I would have thought that maybe the oxides would cause some wild reactions in the clay while it was being fired but it doesn't seem to be. Beautiful colors .
Thanks! I figured these would be ok given the ingredients are often used in glazes. At higher amounts they might cause issues for sure (reacting with the glaze) - but that is just a guess.
Love the 4% IO blend. Even more cool that it added specks to it. Let us know if you sieve the IO and the results you get. Otherwise, it would be great to just add the IO and not have to add any other additives to achieve specks.
Agree - the iron oxide was a very pleasant surprise after my previous speckling attempts. I did not sieve it and I'm not sure what effect I'll get with a larger batch (where I'll be able to mix it up better). But I'll probably try something similar again soon.
Salut Kent. Thank you sharing your results. I was always wondering how oxides would turn out mixed in the casting slip. I'm trying different oxide combinations based on your process. What temperature did you go with the glaze firing? Big hug.
These are all fired to about cone 6.
Thanks for this, I was wondering about using oxides to color slip for slip trailing, and perhaps sgraffito. My question is, will the oxides in the slip affect glaze colors? It would be interesting to do the same tests with white glaze as opposed to clear.
I do like the "frosting" your clear glaze did in the thicker spots and am curious if it does that on all pieces or is it a reaction with the oxides? And, for my purposes, I prefer the 3:7 blend, but think they've all got their merits!
Great questions. It might effect your glaze like a different clay body effects your glaze. If you're glazes are very stable I'd imagine it'd be ok. But like everything inn pottery the only really way to know is to test.
As far as my glaze here, I don't think it was the oxides. I've had it do similar things on other clay as well.
Do the results change after the slip with additives are allowed to set for a day or 2? I'm just curious if the speckling from the iron is due to it not hydrating completely. Have you tried granulated manganese for a speckled effect? (...which has now been placed on my shopping list.)
For my black slip, as recommended in Daniel Rhodes book Clay and Glazes for the Potter (1971 edition), I started with 3% iron and 2% each of cobalt carbonate and manganese dioxide. It works okay. Rhodes recommends experimenting with different ratios for black. I'm trying 3% cobalt carbonate to 2% each of iron and manganese, just waiting to fire them. I got a very pleasant golden brown with 3% yellow ocher. From what I've read and picked up from John Britt it is better if an iron rich pigment like an ocher or clay like Cedar Heights redart is used because raw iron oxide can cause the clay to lose some plasticity. Thanks.
I never did much follow up with this (it's on my list!). Granulated manganese sounds interesting, but no I haven't tried it. I was just winging it here, but it's great to know about other recipes out there. I have done some other tests (off camera) with iron in my clay body and I have had some issues (partially from over firing) but didn't notice anything specific about plasticity.
Which IO did you get and where? There is Brown, Red, and Red Spanish Iron Oxides. Thanks
It is red iron oxide and I got it from my local pottery supply shop.
Hi! Is this cone 6 oxidation? They look beautiful!
They are - fired in my own kiln I rebuilt here on the channel
looks amazing the black ones. but cobalt carbonate is not possible to use in pottery due to its toxicity, am i right ?
would it also work to have a clay body and use this slip as a glaze ? just to dip body in slip not to color all the clay body ?
The inspiration for this was a glaze recipe actually. And yes I suspect you could do it as a thin layer of colored slip over regular slip as well.
In my understanding, cobalt is routinely used for cookware as long as it's sealed under a glaze (glass). Raw cobalt is labeled as toxic substance, although I am not certain how much. LD50 = 640 mg/kg (Rat) in a safety data sheet. unitednuclear.com/PDFs/SDS_CobaltCarbonate_OK_UNS.pdf
hello, what was the final temperature you birn them ?
They are fired to cone 6
I added 1% copper on my slip and waiting for result. I wonder what will happen if I add cobalt oxide to the clay directly… I didn’t research enough other than this video before I experimented, so I’m praying for happy accidents 😅
Hopefully it turns out as you desire! The best way to learn is to test things out for sure.
@@PotterybyKent ahh chat GPT said the same thing :)
🤣
Hopefully this isn't news to you, but I'd be wary of cobalt rich clay bodies as its generally toxic. Although I'm sure this depends on what form it comes in (i.e. carbonate, oxides), so there may be "safer" ways to work with it. I'd mostly be spooked about all the cobalt-clay dust floating around.
It is of course wise to keep clay dust down in general. If you have any good links about the risks of cobalt specifically, that would be great.