High Bridge Pottery

If you put a cone04 in a cone5 firing you will probably end up with it sticking to the shelf unless you are making a cone pack with a bit to catch the melted cones in.  Turned out useful for problem solving this time but I wouldn't normally include an 04 unless you make something to catch the melting cone that's not your shelves.

It sounds like you are saying the 04 firing cones are not right but they sound bent the right amount to me. Are you sure you did a cone5 firing and not cone05 as having the 04 start to bend sounds like you did cone05 by mistake.

It sounds like you are saying the 04 firing cones are not right but they sound bent the right amount to me. Are you sure you did a cone5 firing and not cone05 as having the 04 start to bend sounds like you did cone05 by mistake.

I could certainly get by with a 4 segment program and £400~ extra just for more segments seems like a rip off unless it has more extra features.
 
My typical bisque would be 200c per hour to 100c then hold at 100c for 30 min. 150c per hour to 1000c then hold at 1000c for 20 min which would be the 4 segments.
 
A glaze firing doesn't really need the first hold so for a cone 10 firing it would be 250c per hour to 1180c then 60c per hour to 1280c and a 20 min hold at 1280c. You don't have to hold at the end but they can help to even out the temperature in the kiln. You would change the last ramp segment depending on which cone you want as cones are specified as a rate of climb (either 60c per hour or 150c per hour) for the last 100c of firing to a certain temperature.
250c per hour to 1180c may be too much for thick work or large platters and end up cracking them so something like 100-150c per hour would be better.
 
You could even add a controlled cool to the glaze firing as my example above is only 3 segments. Cooling slower than just turning the kiln off is good for crystal growth, if you are looking to get into proper crystaline glazes then I would probably go with the 20 segment. Not something I have tried myself but I have read they need very particular firing profiles on the way up and down to get big crystals.
 
In the end it all depends on how you like to fire. More segments will give you more ways to try and solve issues with your clay and glazes but from my experience you never need the firings to be overly complicated with different ramp rates and holds.
 
 
 
 
 

Looks like it's here http://www.cressmfg.com/wp-content/uploads/B23H-240-VAC.pdf
 
PS  Broken link showed as
... and a google search for "B23H 240" (with the quotes) found it (even though access to the enclosing directory https://www.cressmfg.com/wp-content/uploads/ is forbidden).

It sounds like you are saying the 04 firing cones are not right but they sound bent the right amount to me. Are you sure you did a cone5 firing and not cone05 as having the 04 start to bend sounds like you did cone05 by mistake.

Hi all, 
A quick update.  I sanded the pots and refired.  The bumps were white and hard in texture.  Somewhat difficult to remove.   I was able to cover them with glaze, but the finished results (where my brush strokes are visible) are not to my liking.  
I have put a fresh load in the kiln today (that I glazed a few days ago). I noticed when putting them in that there were some hard dots on one of the plates.  These wouldn't bother me in a dipping glaze (they would melt and blend in) but I'm wondering if in Stroke and Coat, with its lack of movement, these are the culprit?  Maybe they are bits of dry glaze that I've picked up during a long painting session? Maybe they are small pieces of dry glaze from the bottle (I do try and get every last bit out!) 
So, my working theory for now is that these lumps may actually be from the glaze. This time I've rubbed them out with my finger before firing.  Hopefully I'll see better results after this firing! 
K

I think it's just an optical illusion making them look like craters. If you look at the rim in the lower right the light source is also coming from that direction and the rim is casting a shadow onto the plate.
 
They don't particularly look like blisters to me. I am guessing you would have noticed all the bumps when glazing if it was some chunks in the glaze but worth sieving through 120mesh just to make sure. Maybe you caught a kiln brick putting a shelf in and knocked some debris onto the ware? You could try sanding them, might give you an idea if they are solid chunks or filled with air?

I think it looks a lot better, less cluttered and better formatted giving you the 5 most recently updated topics instead of 5 newest posts which could all be in the same topic.

I think it looks a lot better, less cluttered and better formatted giving you the 5 most recently updated topics instead of 5 newest posts which could all be in the same topic.

In my recent glaze tests I have found 20% kaolin 80% frit will suspend really well for at least a few weeks to a month whereas 10% kaolin 90% frit will be trying to hard pan in about 12 hours.

Ah!
Thanks Johnny, thanks HB!
How's it look now?
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I spent a couple of hours yesterday morning running some screen printing tests. I'm using a 110 mesh screen, Speedball underglazes, and raw Xuan paper. My findings:
- Speedball underglazes come fairly thick in the bottle, so with no modification they actually print pretty well for 1-2 prints. However, by the third print the underglaze would stop going through the screen and it would just print water. The thicker the underglaze the worse it got. If I washed off and dried the screen, then it would print again. I think the underglaze must be sealing up the screen.
- I don't have any guar gum or dextrin in the studio, but I do have CMC gum and Veegum T, which together are fabulous for suspending glazes and making them brushable. Typically I would make a syrup out of them, but I didn't want to add too much water to the underglaze so I mixed it up like thick snot- 2 tablespoons of CMC and 1 tablespoon of VGT to 1 1/2 pints of hot water (normally would use 1 gallon of water). Let it soak (overnight if you have time), and mix it with a stick blender.
I added 1 teaspoon of the snot to a pint of underglaze and ran a dozen prints without any problems. I also thinned out the underglazes a bit and was much happier with the thickness on the paper. No need to let them stiffen up at all. In fact, Speedball underglazes are a bit too thick in the bottle. I'd seen people say it should thicken up to a toothpaste consistency, but I didn't find that to be necessary or desirable.
- I was concerned that the CMC gum would make it more difficult to transfer, since in a typical application the gum makes the underglaze hard and resists water (which is why I always recommend applying underglazes to leather hard and bisque firing before glazing if you're working with dipping glazes). With the transfers they worked much, much better with the added gum. Great release from the paper. I lay the transfer on the leather hard pot, dab it with a wet sponge, then lightly roll it with a little brayer.  I'm doing some bold patterns, not thin line work, so it's easy to control how complete the image transfers by how long I leave the transfer on the pot.
- The raw Xuan paper is very fragile when wet. You have to be very careful about rubbing it when it's sitting wet on the pot. I've got some half raw coming and I'll see if that holds up better.
EDIT: Forgot to add- I have tried making the transfers with newsprint before, but I don't like how much the paper wrinkles as it dries. The underglaze was also more likely to flake off when dry. I'll try it again with the new gum-added version later this week and see if it behaves any better. The good thing about the newsprint is that it's much more durable than the Xuan paper.

All functional pottery is haptic. Feedback by touch. 

FeO is certainly a much more powerful flux but Fe2O3 can help with melting. I don't think you are missing anything entirely, there's quite a fine line/small area of chemistry that will make a good matte glaze as you have found out by removing the iron oxide.
 
All the B2O3 Fe2O3 Al2O3 oxides are a bit weird and can act as fluxes and stabilisers. Can be called intermediate oxides or amphoteric oxides.

Dunno if it would work but you could put them in a box with an ozone generator, just be careful not to breathe the O3.

Nice! 0.3:0.7 is often considered an ideal range for likely durability.  When the ratio departs significantly especially for excess alkali >0.3 it may not be durable. Some reading here:  https://www.ceramicmaterialsworkshop.com/uploads/5/9/1/2/59124729/nceca_2012-  @High Bridge Pottery (the glass former / flux debate emerges again)
So in and around that ideal range …..generally a decent ratio.  0.16 boron at cone 6 also good as shown by Katz and Dr Bill Carty, pretty linear findings below:
https://www.ceramicmaterialsworkshop.com/uploads/5/9/1/2/59124729/katz_tf_boroninglazes_0912.pdf

The Gloss line
Or matte line,  in Stull which is relative - is a Si:Al of ratio of around 5:1 or less and is regional within Stull, trending toward gloss for his glaze at 7:1 and for him highest gloss.
so pretty good picks thus far, my question and caution was very high alumina levels and how did you get there. Things melt by composition though so as the alumina increases so likely does the cone it melts at. I could only find two similar mattes at 0.7 alumina so yours is interestingly high, higher than these and may not melt effectively at cone 6. Old forge below, Si:Al in the 4:1 range and 0.62 alumina.
so nice work, the worry would be its just under melted and testing it to cone 7 or 8 would yield a better melt. Still wondering how you got to 0.74 though.
Old Forge

Only two maybe three similar at 0.7 Al @ cone 6

FeO is certainly a much more powerful flux but Fe2O3 can help with melting. I don't think you are missing anything entirely, there's quite a fine line/small area of chemistry that will make a good matte glaze as you have found out by removing the iron oxide.
 
All the B2O3 Fe2O3 Al2O3 oxides are a bit weird and can act as fluxes and stabilisers. Can be called intermediate oxides or amphoteric oxides.

+1 for Ozone removing ALL of the odor (100%). Reasonable precautions of course - it is an irritant. The good news it’s used for water purification, removing smoke smell from fires, cars with years of cigarette smoke etc…. So extremely useful.
More good news, It’s hard to make more than about 3-4% concentration of O3  and it reverts to O2 in a fairly short time. If you set this up outside, then a box or simple plastic garbage bag is ideal. You do not want the generator to recycle its own output so basically a way to blow ozone / fresh air and let it leak out naturally.
Humans can smell extremely low concentrations of Ozone which contributes to its relative safety, sort of like mercaptan in natural gas products, most people can smell it very quickly. So if you do this, do it in a well ventilated area (outdoors) and stay clear while operating. 10-15 minutes exposure is often enough to remove any trace of odor and 30 - minutes post ozone production is often enough for all the ozone to revert to oxygen on its own.  A decent ozone generator ought to have specific warnings so read and follow all precautions for sure. 

Dunno if it would work but you could put them in a box with an ozone generator, just be careful not to breathe the O3.

Dunno if it would work but you could put them in a box with an ozone generator, just be careful not to breathe the O3.

I picked up a little Evenheat test kiln last Fall and finally got around to getting it up and running this week. It was in brand new condition, only fired a handful of times to low fire temps, but it was a cone 8 kiln, not ideal for all the cone 6 firings I'll be doing in it. So I talked with Euclids and had them make me some custom elements that bumped it up from 2000 watts to 2700 watts, a 35% increase in power. It should have great element life now. It was originally set up for 120V service at 17 amps, and with the new elements it's set up for 208V 1P service at 13 amps (wired in series). I gutted the control box, removing the Kiln Sitter and wiring, and installed a terminal block that connects the elements directly to the power cord. I don't need the sitter since I'm using a wall mounted digital controller. The controller has a Genesis Mini controller and a solid state relay- you can see the heat sink on the left side of the control box. I've been using this box for a few years now and it works great. It was originally an Orton Auto-Fire, but I modified it a couple of years ago to work with the SSR. I also put the thermocouple in a protection tube.
I had a successful bisque firing yesterday, and I'm running a cone 6 glaze firing today. I don't expect any problems, but it's still a bit stressful since it's a new setup. Fingers crossed!

That's true you could make them all 1.44 ohms instead on 240v and get 16.6amps and a 4kw kiln instead of 15 amps and 3.6kw. Looks like the controller has a 30amp relay so that shouldn't be a problem on the relay either and give you additional room for wear.
What size is the breaker on the kiln? 16.6amps +25% does just take you over 20 amps but it might be bigger anyway.

You might want to pick an original wattage to match and establish the new resistance to the original design using his current operating voltage. This way he will have the amount of designed heating energy available.
 
When electric kilns wear by about 10% they usually have trouble making top temperature. In this case since this is a very small kiln electrical and load, bumping this to 4000 watts likely has no effect on his current wire and breaker and could provide additional room for future wear.   Just a thought.

Good to know they are all the same besides the hairpin length. It can be tricky to get an exact read on these things.
 
Having them all at 2.2 ohms means the kiln is drawing just over 10 amps on 240v supply  so I am not surprised it wont reach top temperature/get there slowly. I would maybe confirm it with whichever company but the basics should be voltage/amps = resistance so 240/15 = 16 ohms for 10 elements in series and 1.6 ohms for each element.