High Bridge Pottery

I am thinking the confusion arises from the lack of explanation of cones. While their chemistry is established they indicate by bending so not really fully melted. A cone 4 cone ground up and fired to cone 8-10 turns out to be a fully melted glaze. At present there is not a straightforward exact predictor of when a composition will fully melt. Stull did his work at cone 10 I believe (likely closer to cone 11 today). His map was for a very specific flux ratio and his glazes. Katz showed a reasonable correlation at cone 6 and lower further incorporated boron as a means to lowering the melting temperature. Sue McCleod presented a cone six version of this at a2018 NCECA (Google Sue McCleod and Stull. Stulls map does not predict the temperature something melts at. Higher melting temperatures would progress from left to right and upward in relative ranges. Limits are these tested ranges, but are approximate guidance Testing is generally the only way to know with reasonable certainty when something will fully melt.
Advanced knowledge of durability is a Katz thing where certain flux ratios may be an indication of durability.
I think the simple answer is cones fully melt 4-5 cones higher than their rating. I don’t think the author clearly represented this in the cited link.
I would also suggest that much of pottery is understanding the variability and by experience important trends. It is somewhat very exact and scientific but verified through testing.

Callie, 
a story which has information about a clay in water: 
long long ago, but not to far away, I was still assigned to the refinery when one of the plant cooling systems was changed from deep clean cold water wells to river water that had a small but visible amount of yellow river clay suspended.   Shortly after the switch to river water, the plant heat exchangers began to plug with clay and the exchangers had to go off line to be cleaned (not an easy or low cost task). 
The lab was trying to find why the plugging was taking place and they were not finding anything about why the system was being plugged.  
A lab technician had put a bottle of the river water in the window to watch it over time.  After month nothing had changed, the clay in the bottle of water was still suspended.  Later on, someone decided to clean the window shelf and set the bottle of river water into the sink which had some warm water flowing through.  When the someone picked up the bottle to it back to the window shelf,   he noted that all the clay was now at the bottom of the bottle and the water was clear; and he came upstairs to tell me what he had found.  
my recommendation is to heat the slop water a little bit and see what happens.
if your clays are like my south Texas river clays, boiling is probably not needed. 
LT

Sometimes the trick is to mix it up again to re-suspend the largest particles as when they settle they pull a lot of the fines with them. Not sure about very thick slips, only really used the technique for getting glazes to 1.7g/ml
Calcium will certainly help flocculate slips.

Even at $100/pound, say you put 30 grams of glaze on a mug and 3 grams of that is tin it's only 66 cent a mug in tin.
I don't let it put me off using it, I like tin  

Even at $100/pound, say you put 30 grams of glaze on a mug and 3 grams of that is tin it's only 66 cent a mug in tin.
I don't let it put me off using it, I like tin  

Re-reading Digitalfire the second paragraph seems relevant..
Glaze Shivering
https://www.digitalfire.com/trouble/glaze+shivering
Shivering is the opposite of glaze crazing, the fired glaze is under compression and wants to flake off the body, especially at edges. However the route cause is a mismatch in the thermal expansions of body and glaze, thus the process of resolving it is similar as for crazing. It it much less common because glazes tend to have a higher thermal expansion than bodies and because they can tolerate being under compression much better than being under tension. Of course, if a glaze is under compression on the inside of a vessel, the body will be under tension and this can cause failure of the piece.
When the body-glaze interface is not well developed an overly compressed glaze will be able to release itself much more easily, especially on the edges of contours. This can be the case, not only with low fired ware, but where engobes or slips are being used under the glaze. If the engobe does not contain enough flux to firmly adhere it to the body and develop hardness, it will not be able to bond to the glaze well.
PS Time for some rim-shaped test-tiles?

It a tricky one to decide, will the initial cost to get an electric kiln up and running save you money in the long term with lost ware and time you could be doing something else. 
 
I have semi automated a gas kiln adding a controllable valve onto the pipe but that is not the easiest thing to do. It just meant instead of turning it up every 20 minutes the computer did that for you. There was no brains really, the first firing I did have to turn it up via the computer and record what was set and run a simple program to repeat that for me the next firings.

After looking at the manual posted in the other thread this controller seems a bit weird. T1 is the time taken to get to the NEXT temperature not the C1 temperature. That seems backwards to any controller I have programmed. 
C1 0020c, T1 0030m
C2 0100c, T2 0030m
C3 0100c, T3 0600m
C4 1140c T4 0100m
C5 1240c T5 0000m
C6 0020c
 
That should go from room temp to 100c in 30min and hold at 100c for 30min. Then it takes 10 hours to get to 1140c (you could speed that part up) and then up to 1240c in 100m (60c/h)

After looking at the manual posted in the other thread this controller seems a bit weird. T1 is the time taken to get to the NEXT temperature not the C1 temperature. That seems backwards to any controller I have programmed. 
C1 0020c, T1 0030m
C2 0100c, T2 0030m
C3 0100c, T3 0600m
C4 1140c T4 0100m
C5 1240c T5 0000m
C6 0020c
 
That should go from room temp to 100c in 30min and hold at 100c for 30min. Then it takes 10 hours to get to 1140c (you could speed that part up) and then up to 1240c in 100m (60c/h)

It's my zero3 fritware clay, kiln is just a 40 litre rust bucket.
 
 
I would go with the cone program as it may dynamically alter the firing depending on how it keeps up with the rate of climb. Do skutt controllers do that? 

Wollastonite has a much lower LOI than whiting (1.6% vs 43.9%) and has a lower thermal expansion coefficient (9.0 vs 14.8) (data from DigitalFire).  Wollastonite also provides silica in addition to calcium.   My glazes are high silica/low expansion by design, and wollastonite gets me there.  And finally, Wollastonite cost me $0.59/pound the last time I bought it, whereas whiting cost me $1.17/pound.  I'm sure I could rework my recipes to substitute whiting, but there is a certain amount of inertia involved in doing that, as I'm generally happy with the way my glazes are behaving on my clay.

If you click on the create option in the menu then choose new material you can add it that way if you have the frit analysis.

If you click on the create option in the menu then choose new material you can add it that way if you have the frit analysis.

My fingers! Seriously, they are my favorite pottery tools. 
Betty 

Didn't realise Hulk had found the right diagram ages ago .
 
I don't think it's a good idea to use a 40amp breaker if they suggest 10. The 250v fuse or something is connected to the coil that switches the relay and you should leave it there.

Check to see if this Operating Manual matches your unit?
There's wiring diagrams at the end.
Note the thermocouple spec, page thirteen.
See also the current/power specs...
Topworker P59750 P59760 P59770 P59590 manual A.pdf (wsimg.com)

Trying some frits as glazes, fired to 1100c (2012f)

Trying some frits as glazes, fired to 1100c (2012f)

No reason you can't put the water into the old glaze bucket to start with. I agree with sieving once unless you have a specific reason for doing that.

No reason you can't put the water into the old glaze bucket to start with. I agree with sieving once unless you have a specific reason for doing that.

No reason you can't put the water into the old glaze bucket to start with. I agree with sieving once unless you have a specific reason for doing that.

I finally got around to doing a few glaze tests and brushed some on these mugs. Can't feel any texture through the glaze so pretty happy with the results as I didn't do any cleanup on the mold print.
 
Need gum for brushing, seem to have lost mine.
Need to go back and work on my clay, maybe.
 
The clay is great except it still takes 1.5-2 hours to cast the larger mug and it likes to hang onto bubbles.
Fires like a dream, bisque in 4 hours (20 min to 100c, hold for 20 min then 3h to 800c and hold for 20 min) and glaze in 5.5. I could go faster on the glaze but after 800 my kiln stops climbing at 250 c/h. At 1000 to 1100 it can only manage 80 c/h but that's ok for hitting 1100 cone03.

No reason you can't put the water into the old glaze bucket to start with. I agree with sieving once unless you have a specific reason for doing that.