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Min
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Posts posted by Min
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8 hours ago, Bam2015 said:
Maybe I should start with a new recipe using either Custer and/or Minspar first and test that? If I like that then how would I make it less glossy?
Link here to MC6G alternate glaze recipes using Custer or Minspar that Hesselberth and Roy put out. I don't know how old your Custer is or what the analysis for it is, maybe try a small 100 gram batch if you decide to use Custer before mixing up a bucketful. There is also a version of it using Minspar 200. On that link click on the "Mastering Cone 6 Glazes" tab then on "Glaze Reformulations".
Unfortunately it isn't a simple matter to take an existing glaze and add something to it to make it less gloss. Are you using it as a clear glaze or adding colourants and/or opacifiers to it?
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How comfortable are you working with glaze chemistry?
This is one of those questions that can have vastly different levels of complexity in the answering.
Also, are you using G-200 spar or a different feldspar now that the original G-200 is no longer available?
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Have a look at the cone 6 engobe recipes here. To make them more glossy increase the flux, in this case the recipe uses nepheline syenite plus frit. An earthenware clay should work too if you are okay with the slip not being white, try a blend of earthenware, kaolin or ball clay and nepheline syenite, silica and frit. If you don't have access to a frit try 5% borax (dissolve it in hot water first), this will precipate out of the slip over time so don't make a big batch of it.
It's going to take some testing to get a good fit between your claybody and the slip with the amount of gloss you are looking for.
Yes, I would probably add some deflocculant, if sodium silicate is what you have then try a tiny bit of that. Less water in the slip results in less shrinkage thereby decreasing the chances of it cracking while drying.
- Callie Beller Diesel, Hulk and Gonen
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Another wonderful resource are the Phil Berneburg videos from Washington Street Studios.
Link here to all the Youtube videos from them, scroll down to the ones on glaze chem for potters, geology, glaze defects, clay and glaze testing etc. Really good info, all free.
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Have a look at vitreous slip or vitreous engobe recipes. When you put the slip on the pot will make a big difference in the composition of the slip/englobe. The drier the unfired clay is the less plastic materials you want in it to prevent it cracking or shelling off the pot while firing. If you are applying the slip to bisque ware then you need very little raw clay in the slip, more along the lines of an underglaze than a vitreous slip.
When are you applying the slip?
- Gonen, Hulk and Callie Beller Diesel
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@Harold Roberts, thanks for sharing your recipe, looks like a nice claybody.
Yes definitely, care must be taken when firing manganese to use a very well vented kiln, (whether in a glaze, slip or claybody) as the fumes from manganese are toxic. As to the colour difference I suppose that's a question of personal preference.
@Localpotdealer1234, if you fire in an electric kiln it will be firing in oxidation or a neutral atmosphere. If firing in reduction then yes you can get iron speckling (depending on the claybody).
Image below taken from Digitalfire, same claybody with the same glaze fired to the same cone. Test piece on the left oxidation fired and reduction fired on the right.
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Beth Cavener Stitcher shares lots of her info about the type of epoxy she uses, mixing tips, using it as fresh as possible, storing unmixed epoxy in the freezer, which are slower to age and turn yellow etc. She is really generous with the info she shares. Link below to her page discussing this.
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5 hours ago, Mariap said:
I do not have control over kiln temp, I am firing in my school's kiln.
Ask the person firing the kiln what cone they fire to and if there is a cooler part of the kiln you can try a test tile in to see if firing the Amaco LM11 cooler helps matte the glaze.
BTW, zircopax is an opacifier, I haven't found it will matte a glaze with typical amounts used, it will whiten a clear glaze though.
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15 hours ago, kevinpleong said:
I appreciate cone 10 because the clay is completely vitrified at that point.
When ceramicists use the term vitrified it usually has a different definition than a person who works with glass. It's my understanding that the term "vitrified" for a glass worker / gaffer / glass blower/smith etc means that the materials have been transformed into glass or a glassy substance by heat and fusion. Potters have adopted the term vitrified to encompass not only glazes but ceramic bodies as well.
There can be confusion with this. Given that claybodies contain crystalline structures as such they cannot by definition be transformed into a glass or glassy substance.
IMHO a better description of zero porosity vitrified claybodies would be a claybody fired to maturity with zero absorption. Is zero absorption necessary for functional wares intended to hold liquids? Nope, in fact there will be a high number of stoneware or earthenware bodies that will slump and or bloat well before they reach 0% absorption. Are these bodies with higher than 0% absorption still suitable for functional wares intended to hold liquids? In many cases, yes absolutely they are. Under approx 1.5% (one point five) absorption bodies are used by many potters for such usage with no issues.
Fritware bodies fired in the earthenware range can have absoption figures down to zero as can midrange bodies or any temp/cone you would like to fire at. Are cone 10 bodies vitrified just because they are fired to cone 10? Maybe yes, maybe no. Fire a raku or sculpture body to cone 10 and it's absorption will probably be well be over 1.5% still. Overfire a claybody and after it's densification is maxed out the absorption/porosity will actually increase as the body breaks down.
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I have dipped wide shallow bowls with magnets, they start out as 5 lbs then get trimmed down. I wax the liner glaze with the shallower ones. I haven't glazed over an entire bowl inside and outside with magnets. Have you seen the way Hsin-Chuen glazes inside large bowls with a plastic bag of glaze then pours the outside? Would this work better for a single glaze like you are doing?
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2 hours ago, Callie Beller Diesel said:
@Min I was looking at these ones from the Canadian Lee Valley site, because they have the hook attached. I was fighting with glaze tongs and some serving dishes in a glaze bath about a month ago, thinking there had to be a better way.
That doesn't look much stronger than the flat ones I mostly use. How deep are your serving dishes? What shape / how heavy are they? If it's a bowl shape and not too shallow I'ld use a stronger fishing magnet outside then you only need a thinner magnet inside so you don't land up glazing it along with the pot. I have one I scrounged from my husband, which I have since lost in the move, river in South America has a few with good reviews, could return it if not strong enough.
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2 hours ago, Juxtaposie Jen said:
I almost wonder if it might be too strong
Could be but would be a good experiment to try! Let us know how it works if you try it.
BTW it seems your link isn't working.
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35 minutes ago, Callie Beller Diesel said:
Like Bill says it depends on how thick the floor of the pot is. Mug in my image above was thrown from 1 lb 2 oz + weight of handle, no trimming, base is about the same thickness as the walls which you can see at the top. I use these 3/4" ones, average mug uses 3 magnets. Doesn't matter how they are split up, 1 inside and 2 outside or vice versa. So, just ball park math Lee Valley says 3/4" ones will lift a 22 lb block so with a fairly standard thickness of pot base 66 lbs of lifting power for a bisqued mug weighing approx 1 lb.
If you need more than 4 of the round ones I would suggest using a rare earth fishing magnet instead, less chance of chipping them. Fishing magnet on the outside, single round magnet on the inside.
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Hi Maria and welcome to the forum.
If you have the option to fire a little bit cooler it just might be enough to use your existing glaze. Are you firing to cone 05 now or hotter or cooler? Also, how is the kiln cooling? If you slow down how fast the kiln cools this can have a dramatic effect on how some glazes cool.
Can't help on suggesting a commercial matte glaze, hopefully someone who uses them will chime in.
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11 hours ago, Babs said:
So they elease from the glazed ware ok?
Yes, like Mea said once you remove the magnet on the outside the inside one falls away. If the inside glaze is soft then just drop a scrap of newsprint into the pot first and set the magnet on that.
Another point about why I use a twist tie with the inside magnet is so I can reach the magnet without touching the inside of the pot. Bend it shorter for short forms. For wide open forms like bowls just using the magnet bundle is enough.
Use enough magnets to get a strong bond between the inside and outside magnet(s), needs to be strong enough to hold together while removing the pot from the glaze bucket (with the suction from glaze) but not so strong that they are difficult to remove.
Rare earth magnets are strong but they are fragile. I've tested ones from different suppliers, I have found there is a difference in the strength of them. They can break but are still useable. I have read that if you have a pacemaker then it's best not to use them.
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Lots of good suggestions for glazing tips in this thread. I'll start a new thread with another method using magnets here as it probably should be in the Studio Operations section.
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Glazing tools and tips brought up in this thread, starting a new thread as this should probably be in the Studio Operations section.
This is how I use magnets when glazing, no tong marks, drips or finger marks on the glaze. It’s been a game changer for me with the pots I dip. Flat bottoms on pots work the best but you can do rounded bottoms, it’s just a bit less stable while dipping.
- liner glaze the inside like usual
- rare earth magnet(s) wrapped in a scrap of plastic with twist tie inside the pot. twist tie is used as a handle. keep the twist tie below the rim of the pot
- another rare earth magnet(s) with a flat head bolt for a handle on outside of pot
- fishing magnet used for larger pots, they come with a handle so don't need a flat head bolt for a handle
-number of magnets needed determined by pot weight (and base thickness). I try to use just enough to be adequate to pull the pot from the glaze but not more or else they can be fiddly to remove. for tiny pots I use 1/2 pieces of broken magnets.
- hold the pot by the bolt and push the pot into glaze then lift it out. (rotate the pot slightly to have any excess glaze roll around the rim)
- when the pot is dry enough to touch at base area turn it over and remove magnet(s) from either side. 20 seconds or so for most glazes. I hold the pot on the outside bottom of the pot when flipping over
- you can slide the pot onto the edge of a counter while removing the outside magnet if you don’t want to wait for the glaze to dry enough to hold onto the pot, or stuff your hand inside the pot to move it to a ware board.
- when I first started glazing like this I got a couple blood blisters, don't pinch your fingers, those magnets are strong!!!! I use the ones from Lee Valley tools. (to separate them use an edge of a counter and push them apart)
Anyhow, that’s it, simple and it works. I tried to think of a way to market the magnet glazing but life got in the way.
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Firing glass on clay has come up a few times on the forum. General consensus of forum members is this isn't a good idea. Several threads on this topic, link below to one of them.
6 hours ago, Oddoneout said:I can only think that since I had wax on the bottom and glaze everywhere else that there must have been water that was not burned off when the glass melted and this caused the rims to blow off.
Don't think this would have been why. Reason why the melted glass has craze / crackle patterning is because the glass expands and shrinks at a vastly different rate than a claybody. COE or CTE (coefficient of thermal expansion), same thing, different name. Sounds like with your original coasters the glass was much thinner than the ones that shattered in your latest firing. This doesn't mean it's safe practice to just put the glass on more thinly, still subject to stresses and the risk of slivers of glass dislodging.
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@Joseph Fireborn was interested in what gave the Black Ice Porcelain from Sio-2 Clay its black colour. From this thread he was told by the manufacturer it is stain plus oxides but not including manganese. SDS for Black Ice Porcelain doesn't give any clues.
- Rae Reich, Joseph Fireborn and Hulk
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Another factor that could make a huge difference in what type of fuel your kiln uses is insurance. Absolutely no way I could get home insurance for a gas kiln, it was hard enough to find an home insurance that covers electric kilns for a home based business. (I use BCAA in Canada) Also, where I live wood burning wouldn't be allowed. Even open wood fireplaces will be banned within 3 years.
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I haven't used them but this place has been mentioned on the forum in the past.
https://www.milestonedecalart.com/custom-decal-shop
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How to make this glaze a bit less glossy?
in Clay and Glaze Chemistry
Posted
Okay, probably the simplest way to tone down the gloss level would be to do a volumetric line blend with a matte glaze. This just means you take equal volumes of your clear and a matte glaze then blend them together in different ratios. Both base glazes need to have exactly the same weight of dry materials and water. Info on how to do a volumetric line blend in this link if you need it.
For the matte glaze recipe you could try the recipe below. It started out as a Tony Hansen recipe that I altered to use Ferro Frit 3134 as you already have that. Probably less than 20% of this matte recipe blended with your clear should take the gloss down enough and still be resistant to cutlery marking.
By doing it this way rather than start testing a bunch of new glazes you are making a glaze that will be predominately your existing glaze, plus you can fine tune how matte you would like it. Do note that the new glaze might have an effect on colourants as the matte is high in magnesium. If you try this please test it first before committing to a large bucket of glaze.