.jpeg.e14571b8528e66a7a9c872fd28550125.jpeg)
Min
-
Posts
5,957 -
Joined
-
Last visited
Content Type
Profiles
Events
Forums
Blogs
Gallery
Posts posted by Min
-
-
6 hours ago, Ben xyz said:
though would like to correct hairline crack I found
You lost me here, the slip has a crack or the pot?
A - I don't know how your glaze would look on the patterning, would have to try a test piece and see.
B - Is it a cone 10 clay or would this be a different piece of work? You can colour the slip with stains or a darker firing ball clay if you have one for the next one you make.
C - Using no glaze gives the clearest patterning, this is what Hopper did on the outside of his vessels but be careful if you glaze the inside as you need a really well fitting glaze if you only glaze one side of a pot to avoid dunting / cracking of the pot due to uneven tensions.
Suggestions - make some tests. If you find the contrast of the dark cobalt + manganese and the slip is to harsh try using just a very small bit of colourants, it will still be blue but might not be as dark. Cobalt is very strong, doesn't take much to get blue.
BTW, typo in your oxides, manganese dioxide not magnesium.
-
Is this the type of silica scale you have? (Google image)
I'm wondering about particle size and how you would get the silica scale into a useable mesh size without specialized equipment. With many glazes having a 325mesh silica versus 200mesh makes a difference in the melt. If you can get around that problem safely then to make a glass I'm thinking soda lime glass from soda ash + calcium carb + silica might be a good experiment to start with.
-
Ceramic stains are basically colouring oxides that have been fritted into a safer form for the potter to use and widen the range of colours available. If you have a well balanced stable base glaze then there is a good chance the glaze coloured with stains will be stable if the glaze is well melted and the amount of stain used is within reasonable amounts. Having plenty of silica and alumina in the base glaze, not overloading the boron and firing to maturity all help in creating a durable base glaze. BTW if you are going for a celadon like look you probably won't need 3%.
Robins Egg Blue and Vanadium Yellow both contain vanadium which is quite toxic in the raw form so using a stain to supply it is by far the safer route. If your base glaze doesn't leach with base and acid testing then it's probably okay but the only way to know for sure would be to get it lab tested. I don't know of many people who actually do this.
-
@Kelly in AK, distinction between what is craft versus art wouldn't be a contentious subject at all would it?
It seems the word "craft" is used very commonly and freely whereas "craftmanship" has a higher level of skill implied in the learning of the particular craft it is used in conjunction with. I've noticed in the last 10 years or so an increase in the number of people who work with clay are calling themselves ceramic artists vs potters or ceramicists. Who determines if the work is art or fine art or a craft?
- Kelly in AK, kswan, Pres and 1 other
-
4
-
2 hours ago, Pir said:
Wait, what's MAGMA?
https://www.brackers.com/wp-content/uploads/2010/11/magmainfo.pdf
https://www.brackers.com/magma-miracle-anti-gravity-multipurpose-additive/
If your glaze slurry can't be dried slowly then don't use it, otherwise it is brilliant stuff. If you try it do add the tiny bit of copper as the instructions indicate (if the glaze doesn't have any) as this is an organic product and will rot otherwise. Doesn't work quickly like vinegar or epsom salts etc, need to leave the glaze alone for about 8 hours for it to work.
-
I have a cone 10 glaze with just under 65% nepheline, some dolomite and zircopax plus just under 5% ball clay. It sinks like a stone in no time, however I've gone a year between uses of it and it still stays suspended with some MAGMA. This stuff will float rocks as @Mark C. often says.
The 5 whiting aka calcium carb will mess with the vinegar. Carbonates + vinegar = CO2 gas, might be enough to negate the effects of the vinegar. Another thing you can try is calcium chloride instead of epsom salts. (it's sold as ice melt)
-
If it is silica then it won't melt at 1200C. Typically are there fluxing minerals in the scale also?
-
@Kelly in AK brought up an Issac Button video and just how much physical work was involved in his making pots. My suggestion for a QOTW comes from Kelly's thread and would be how has the physicality of making pots effected you? Positives and negatives.
- Kelly in AK and Rae Reich
-
2
-
17 hours ago, rebs said:
i actually tried to post a picture, but got a message the file was too large and wasn’t able to shrink it..
Try emailing it to yourself, that should automatically shrink it down then post the emailed picture.
It's the time spend in certain temperature ranges that is important to note when bisque firing dark clay bodies. Need to have time for the gaseous materials to burn out. Chart below from Steve Davis (link here to an article with it) showing a schedule to help prevent glaze faults. Between 1290F - 1650F is when you need to really slow the firing down. Also, don't overload / cram the bisque firing full, clay needs lots of airflow around the pots. This is a very long schedule, reduce or eliminate the first hold time if your pots are dry to start with. Might be able to shorten or speed up some of the other segments depending on your results.
-
Brings up the physicality of working with clay doesn't it? Net gain, probably, but there are side effects for sure.
- Pres, Kelly in AK, kswan and 1 other
-
4
-
Commercial stains usually need some sort of flux to help them stick to the clay during firing. Are you looking for a transparent colour or opaque? Wondering if a slip or engobe might be more effective for your purposes. Re stain / underglaze / matte glaze combinations, too many variables to say for sure what will happen. Example would be an iron oxide wash / stain will get bleached out with a glaze high in calcium or a stain containing chrome will likely be very dry, etc. No nuclear explosions but test tiles are worth testing all your combinations on. If you want a look of flakey paint have a look at some crawl or reticulated glazes overtop of underglazes.
If you could post a picture of what you are striving for we might be able to give more concise suggestions. Also what cone you are firing to plus what kind of firing. (electric?)
Welcome to the forum.
-
5 hours ago, bjorn.lindberg said:
Hello, what is the book called?
Thanks
@bjorn.lindberg, I would send @JolandavdG a pm and ask them since they haven't been on the forum since March. Just click their name then at the top of the page that comes up click the little envelope and follow the prompts. They will get an email letting them know they have a message.
-
The glaze descriptions aren't very clear are they, firing range cone 4-10, no further info, hmmm. Only having one product with an actual glaze image rather than the little coloured dots all the rest have doesn't seem very helpful either. I'm guessing that many of the glazes are from one base with stains added. Think you would be better off finding a clear that fits your clay then adding stains to that.
-
Closest I have seen is Ryan Coppage's electric fired wood ash glazes. Not soda but there is a bit of flashing. Link here to an article from him, it's behind a paywall but you can see 3 pages a month for free. Image from that page below, cone 6 oxidation.
Welcome to the forum.
-
Given that it is probably overfluxed at cone 10 (references below) I would try a couple things. First I would fire some as is in the hottest part of your kiln and measure the porosity, it could just be low enough for your purposes as is. Will likely loose translucency but perhaps that isn't an issue.
If that is a no go then I would try adding 5% nepheline syenite to it. Coleman is so plastic I doubt this will make a significant difference to the working properties of it.
From this link:
From this link:
"These are cone 10R porcelains made using Grolleg kaolin, feldspar and silica. Plainsman P700 (left) has 20% G200 Feldspar. Coleman porcelain (popular among potters in the US) has 30% of the same feldspar. The Coleman porcelain is certainly more vitreous. In fact, it is too vitreous. It is much more likely to warp during firing. And, it is much more problematic with regard to plucking (lower left), foot rings glue to even kiln-washed shelves. But, notice that the Coleman porcelain is not any more translucent than P700 (it appears less so because I could not throw it as thin). So why is 30% feldspar even used? I have a theory: American kaolins do require 30% feldspar to vitrify at cone 10, but not Grolleg. it contains significant natural feldspar, so much so that far less feldspar is needed in the recipe. I think that, in the past, Grolleg was simply substituted for an American kaolin a standard recipe. P700 benefits in a special way by recognizing this different in Grolleg: It dedicates the 10% gain to kaolin, increasing body plasticity. On top of that it adds bentonite, producing a porcelain whose high plasticity would come as a shock to people used to the Coleman body."
edit: I'll go through my bags of old clay and see if I kept any leftovers of Coleman, if I have some I'll fire it to cone 6 electric and measure the porosity just for curiosities sake.
-
@kevinpleong, just for clarification, you are looking for cylinder forms to make slip casting molds? I have used a Lysol wipes container as a large mug form, they are gently rounded at the bottom with straight sides. Neil's idea of PVC pipe is a good one too as it comes in different diameters. You could add soft clay to the bottom to seal it up while casting it.
-
I have fired Laguna Dover White to cone 6 with no problems. This was about 20 some odd years ago, don't know if it has changed since then. Fired Laguna B-Mix to cone 6 for about 15 years, no problems.
-
Will keep my eye out for some and give it a go. I can see this working really well for large flat surfaces.
-
14 hours ago, neilestrick said:
I'm not trying to be a downer, but I think your best bet is to contact another potter in the area and see where they get their clay. You could spend a ton of time trying to figure this out and end up not being able to fix it. Most clays are not used alone, but are blended with other clays to achieve the properties you need, and not all clays are good for making pots. The other thing you need to consider is your ability to fire pots. If you can only get to 900C (cone 010), then you're not going to be able to make functional work. Pit firing and other non-functional techniques can make some really great work, though. You really need to be able to get to 1000C in order to use glazes.
@Tina01, firing temperature is a really important point if you are wanting to make functional pots. Have you tried your kiln to see how hot it will go or do you have access to a kiln that will fire hotter than 900C? It would be a shame to go to all this work of creating a useable clay only to find you can't fire it adequately for your intended use. May I also ask if you have glaze materials or commercial lowfire glazes available to you?
-
Might be easiest seeing the info side by side.
When we work on glazes with calc programs we put the recipe in and most often ask for a Unity Molecular Formula (UMF) to show which oxides are present and their amounts. Although we can show the amounts in relation to each other in a few different ways, UMF means the fluxes add up to 1.00 There are other formats we can use also, Molar, RO Unity, R2O3 Unity, Non Unity. UMF and Molar are probably the most common methods.
So, taking the 2 frits that are being discussed, I put 1lb / 454 grams of each frit into the recipe boxes in the charts below. This could have been 1 gram or 1,000,000 grams, doesn't matter, the data will remain the same. See where it says "Auto Unity", this means UMF, that is to say the fluxes will equal 1.0 when added up. Everything else is in relation to the fluxes of 1.0
Now have a look at the percentage column, these figures line up exactly with those of the Ferro Chart posted above. This is the percentage of each oxide within the frit. If you look at your Glazy charts above you can see boron is included in the R2O3.
-
15 hours ago, Bill Kielb said:
Maybe a bit of Right tool, right time actually
Maybe just use some lugs for this, GG probably not the best choice.
Or a chum would work, would prevent pressure on the points that are in contact with the wheelhead / surface that could lead to cracks from the pressure.
-
4 hours ago, mr_glazy_man said:
the boron isn’t low enough to melt both of those
I think you had a typo here, boron isn’t high enough.
4 hours ago, mr_glazy_man said:Tangentially: does Wollastonite typically opacify a glaze?
Wollastonite melts more than whiting + silica but fritted calcium melts better than both.
5% copper oxide is a heck of a lot, do you need that much to get the colour you want? I would suggest trying base glazes without colourants as well as with as the colourants can change glaze behaviour.
-
With all due respect there is more than one way to trim a pot. People got by fine trimming all shapes of pots before Giffin Grips were available, if you prefer to use one then have at it!
Different philosophies as to how and what to teach, doesn't mean one method is better than another, just different. Full disclosure, I don't use a Giffin Grip and have never found a pot I couldn't trim, including the bottom of the type in my avatar. I make thousands of pots a year.
-
Testing and working with wild or found clay has come up a few times recently. I started a separate thread hoping to discuss this here. I started with 3 good links on how to process and test wild clay, might be somewhere to start. Regarding your specific clay this thread will hopefully get you some pointers too. Mica in lowfire clay adds a nice sparkle and acts like grog, helpful to prevent cracking.
I'm reading your post as having three main questions, first how to process the wild clay, secondly how to test it and thirdly how to fire it in your fire pit. Fire pit question could be an entire different thread if necessary, need to fire for longer than 2 hours. What happens when you put a piece of your fired clay into water?
It seems the word "craft" is used very commonly and freely whereas "craftmanship" has a higher level of skill implied in the learning of the particular craft it is used in conjunction with. I've noticed in the last 10 years or so an increase in the number of people who work with clay are calling themselves ceramic artists vs potters or ceramicists. Who determines if the work is art or fine art or a craft?
Hydrophobic surface for spouts
in Clay and Glaze Chemistry
Posted
A very very thin almost not there swipe of clear silicone works too. But you can feel it if you touch it so for me that's a no go too.