.jpeg.e14571b8528e66a7a9c872fd28550125.jpeg)
Min
-
Posts
6,057 -
Joined
-
Last visited
Content Type
Profiles
Events
Forums
Blogs
Gallery
Posts posted by Min
-
-
-
-
Does the underglaze smell at all? Thinking the gum(s) are breaking down.
-
Chrome is volatile, it will flash too. Think of a white glaze opacified with tin, if you have a glaze containing chrome near it while firing the white can flash pink from the chrome.
-
It's flashing from the super high amount of sodium in the glaze. (and probably the cause of the crazing too)
-
If we have a look at the recipe and formula mentioned in the thread above there are some alterations to make to the glaze to get it to melt at cone 6.(info from that thread at the bottom of this post) Either boron (from a frit or Gerstley Borate) or zinc will be needed to flux it enough for midrange.
For boron the obvious choice would be Ferro Frit 3269 as its a boron frit with very low calcium with no other alkaline earths but it also contains zinc. However, it is very high in sodium,( Na2O), and potassium, (K2O), which is likely to increase glaze crazing from their high Coefficient of Expansion (COE). So to adjust the glaze to reduce the COE there must be either Lithium added at the expense of some of the K2O / Na2O or one of the low COE alkaline earths, magnesium, (MgO), would be a good choice. Problem with this is then you are back to alkaline earths washing out the iron, albeit less so with MgO than CaO.
Second problem to address is the colour response zinc can cause with iron. Granted there isn't a great deal of it with Ferro 3269 so this might or might not be an issue if you can come up with a formula using it with lithium to counteract the high COE plus increase the Al2O3 and SiO2 would be necessary to make a workable midrange glaze. Might be somewhere to start if you want a deep dive into glaze chem and testing.
Â
44% North Cape nepheline syenite
34% Potash felspar
20% AB clay
2%Â Kaolin... which is attempting to achieve
0.8 K2O
0.2 Na2O
1.17 Al2O3
0.05 Fe2O3
5.35 SiO2edit: for the purposes of this discussion I have left the flux ratio out of the equation but it should be considered.
-
-
25 minutes ago, HenryBurlingame said:
Do I just need to use softer than normal clay
Yes.
-
16 hours ago, Babs said:
If painting on glaze I wouldn't use clay on its own incase it hinders the onglaze marrying into the glaze. I just use cobalt and water, or for a softer blue a bit of iron. To make it painterly a tad of CMC ...
I make up my glaze from ingredients but the recipe is one of Janet de Boos'sÂ
Google Gerry Wedd an Aussie potter, Brilliant on glaze blue decoration.
@Min can I post that here?
Some folk sinter their pieces first to harden glaze surface then decorate, some spray with starch I believe. I wpnder if spra ying after initial paint at one strength, then paint again, spray again at a different dilution would affect anything
It’s fine to write out glaze or wash, slip, claybody etc recipes  @Babs
-
-
-
This is glaze crawling, happens for a few reasons but in this case it looks like the glaze was applied to heavily. Other reasons for crawling are dirty bisque (hand lotions/oils etc on clay) or a high shrinkage of the glaze from materials within it having high loss on ignition.
As long as the clay doesn't weep from too high an absorption the teapot will be fine to use.
Nice looking teapot.
-
Refires are always crap shoots but if you don't have anything to loose it's worth a try.
I'ld suggest that if you have some thicker glaze (from the side of the bucket where the glazes dry out) take some of that and get it on the bare spots then refire in the coolest part of your kiln.
Â
-
How much experience do you have with glaze chemistry? Do you mix your own glazes or use commercially prepared ones? If you mix your own how in depth an answer are you okay with?
Â
-
Hi Alan and welcome to the forum.
Iron tends to get bleached out by the calcium that is found in most cone 6 glazes. I don't know what is available on your side of the pond but you might want to look at using either a brown underglaze, or a brown and black mix of underglazes, or a ceramic stain mixed with a frit to help it adhere to the pot plus some kaolin.
-
4 hours ago, oldlady said:
a special thanks to Madeleine who first gave me the recipe and has now fixed my mistake. looking through emojis but cannot find one offering a dozen roses.
 just friends helping friends where they can
-
It could be thickness of the paper you are using that is part of the problem, how thick is the paper you have tried? Manila folders or tar roofing paper are both fairly thick and leave a good impression. Also, if your clay is too damp try either leaving the slab dry out a bit before rolling the paper onto it or try dusting it with cornstarch / cornflour.
-
Just double checking your problem, you added 3,000 of whiting instead of 2,000? All other ingredients added as stated, including 3,000 silica? If this is correct then you added 50% too much Whiting.
Not a math genius either but this is what I get...
Add the following to the bucket (hope you have a big bucket)
3134Â + 700
C&C + 900
NepSy + 900
Silica + 1500
Bentonite + 100
edit: Just reread your post, add a total of 4500 silica to the bucket. (3000 that was supposed to be in it plus 1500)
Â
Â
-
A deflocculated slip will contain less water than the same consistency of slip that doesn't contain a deflocculant. A deflocculated slip will shrink less than one that isn't. John Britt video demo's the process well. https://www.youtube.com/watch?v=3an-E0Lk8mQ
Re epoxies, have a look at the process info on Beth Cavener Stichter's site, she is very generous with sharing her process. She seems to favour PC11. https://followtheblackrabbit.com/portfolio-item/materials/
-
-
-
Looks like Laguna lustres are still available at Axner and Plainsman but sold out at a few of the other websites I checked.
https://www.lagunaclay.com/lustersÂ
-
I thought you were referring to the manganese specks, thanks for editing your post. Without knowing what's in the clay it's hard to speculate what is causing the white spots/droplets.
2 hours ago, Hulk said:I'd guess that there's somewhat out of sequence in the sintering/fusing when the clays are mixed together which produces the awesome bloating.
Yes, the whole is greater than the sum of the parts, just as with glazes. (eutectics)
-
Hydrogen peroxide for throwing sludge if it’s stinky. Copper carb for my small tub of Magma glaze additive.
 just friends helping friends where they can
My 50th annual North Country Fair-its been a long windy road -selling ceramics at the North Counrty Fair
in Business, Marketing, and Accounting
Posted
Playing peekaboo Mark? 🙂