High Bridge Pottery

I am not sure why a kiln would trip it as they work by comparing the power going in and out and if they don't match then it cuts the power. In the UK most panels have a GFCI (RCD) that all the power has to go through first before any breakers. Seems better to have one as if current starts flowing through you to ground then it will probably save your life.

Yea, I would try a firing to only 100c first and figure out what's what. Something like 100c top temp, pot F1 set to 5, t.F1 set to 30 min and t.F3 set to 10 min and see what happens.

I am not sure why a kiln would trip it as they work by comparing the power going in and out and if they don't match then it cuts the power. In the UK most panels have a GFCI (RCD) that all the power has to go through first before any breakers. Seems better to have one as if current starts flowing through you to ground then it will probably save your life.

The confusing bit seems to be the pot F1 (%). As you can only set the top temperature I am guessing pot F1 (%) tells it what percentage of the top temperature to go to and t.F1 tells it how long to take. F2 just seems to be a full power ramp up to the top temperature as you can't set it anywhere and t.F3 is the hold minutes at top temperature.
 
I can't figure out what else pot F1 would mean. An example of how I feel it works would be you set top temp to 1000c and pot F1 to 6 and t.F1 set to 6.00 or however many hours and it should go to 600c in 6 hours then full power to 1000c.
 
 

My worst screw up was generating an emotional wound. I know how to load a kiln properly. The mistake I made was in part due to cognitive deficts (memory/acting on flawed recall) , but also  due to arrogence (know-it-all ism/being over confident). My sister made some pieces in a community class. She was very pleased with her stuff and her pieces were really lovely. She actually hauled the glazed greenware up to NH from VA on her vacation.  One piece was a beautiful tray. My half shelves where I put the tray were not aligned at the same level--one was about an inch higher. I placed the tray with one end of it extending over the gap. My sister asked me if it would be OK that way. I assured her it was fine. She asked several times--I wish she had said she just plain didn't want me to do it. Each time I said it would be fine. I fired it like that and of course it warped and was useless. I have no idea what I was thinking or why I didn't reload the kiln to avoid the situation. I absolutely know/knew better.  The worst of it is we have never bounced back or healed from that, because the loss, the disappointment, was just one more in previous and subsequent other problems afflicting our relationship-still unresolved. Apology if TMI.  And just FYI, I'm OK-I've perfected the art of self-forgiveness when such is essential for my own well-being. 

I've been making 3d printed models for molds for glass casting, concrete casting, etc, for about seven years and now delving into plaster mold making for slipcasting. I've never had success making a plaster cast directly from a plastic model. Also, plastic models printed on low to mid-priced FDM printers are always going to need 'post-processing' to smooth out the surface (especially the tell-tale 3d printer striations) and seal it properly.  I use automotive primer/filler paints or Smooth-On's XTC-3d epoxy to fill and sand, then shellac, wax, etc. It's an iterative and time-consuming process but can't be skipped.  Once I print the model (I use Rhinoceros software to design - and check for undercuts within the software), I post-process significantly to get a 'perfect' surface as mentioned, cast a rubber mold (I use mostly Smooth-On Vytaflex 40 urethane rubber), then cast the plaster duplicates from the rubber mold. If I have a concave surface model that is small, say a teacup where it would be difficult to post-process the printed model and/or you don't want to make your knuckles bleed, I take one more step and make a convex positive instead, where I'm then able to post-process more easily an exposed outside/convex surface.  From that I then cast two rubber molds - the first rubber mold from the plastic model, and then the second and final rubber mold from the first rubber mold. When casting the rubber molds, I always use a release agent recommended by the rubber manufacturer. No release is necessary to cast the plaster from the rubber mold.  The process is much work, but it's worth the effort, if not for the learning when the failures happen (usually design-related)! 

Just or the record, there are several 3D printing pages at digitalfire.
3D Printing a Clay Cookie Cutter-Stamper https://digitalfire.com/video/3d+printing+a+clay+cookie+cutter-stamper
3D-Printing https://digitalfire.com/glossary/3d-printing
3D Design https://digitalfire.com/glossary/3d+design
3D Printer https://digitalfire.com/glossary/3d+printer
Project: 2019 Jiggering-Casting Project https://digitalfire.com/project/15

The key to Murphy's is to create a lather. (with a brush) Then wiping away the excess lather with a sponge, then wiping away excess bubbles with a dry brush. Do this three times and you'll have a nice "oil-like" surface. (Which flakes off/dissolves in a few days.)
My concern with pouring plaster against wet Murphy's is that the wet substance MAY absorb into the plaster surface. You might have a different experience, however?
Another option is to use a food safe silicone spray. In the US there is a product called PAM. In another mold making forum this was mentioned as an effective release material when pouring plaster onto nonporous surfaces.

I have been 3D printing some forms to cast in plaster but found it time consuming setting up cottle boards every time I wanted a new mold. Started working on getting a form that I could pour plaster directly into to make the mold.
They turned out quite good, I just need to find the right release agent to use, tried a beeswax polish and soft soap but neither seem to work as well as I would like. Going to buy some proper mold release or other spray that will let the plaster release nicely but my initial tests are promising  If anybody knows a good product I could use as a release agent please let me know, using PLA to print.
 

When I've used Murphy's soap I used a quite damp sponge and applied on a thin layer. I let that dry then repeat with a bit of light buffing between coats. Keep adding coats until water beads off the surface. I then bought some mold soap, for me it works better. (I used Murphy's on a whole fish once, as the plaster heated up it made a nasty smell of hot stinky fish combined with Murphy's, Can't use the stuff now without gagging a bit, probably too much info)

Tony Hansen strikes again.
in https://digitalfire.com/picture/2463
The incredible utility of 3D printing master handle molds
As a parting-agent I use Murphy's Oil Soap on the 3D-printed PLA mold, this makes it fairly easy to extract the freshly-cast plaster molds (the sidewalls have a draft of about 5 degrees).

I have been 3D printing some forms to cast in plaster but found it time consuming setting up cottle boards every time I wanted a new mold. Started working on getting a form that I could pour plaster directly into to make the mold.
They turned out quite good, I just need to find the right release agent to use, tried a beeswax polish and soft soap but neither seem to work as well as I would like. Going to buy some proper mold release or other spray that will let the plaster release nicely but my initial tests are promising  If anybody knows a good product I could use as a release agent please let me know, using PLA to print.
 

I was reminded of a different approach to the same 3D printing idea. It used sacrificial 3D prints, and produced moulds with minimal  excess plaster.

3D Printing a Mold for a Slipcasting Mold
https://www.instructables.com/3D-Printing-a-Mold-for-a-Mold/

Obviously horses for courses, but maybe something for your notebook.

Picture below has been cropped to fit format: actual clay size is 7” x 4” x 4”. Sample was saw cut and wetted to illustrate layers/ color/ and grain. Sample was flipped upside down to capture color variations. The orange/gold color on top is actually the bottom of the sample.
A wild clay sample can tell you a lot just by looking at it. Obviously this is a sedimentary clay because it has three distinct layers and colors. The bottom layer is thin, and is noted by the cleavage crack at the bottom left corner. The top layer is granular and light orange/gold in color, which denotes the presence of iron disulfide (iron). This sample of iron disulfide is light in color, which means total iron content is in the 3-4% range. As the percentage of iron goes up; the color will become deeper and deeper. Naturally occurring magnetite (iron) usually presents medium to dark gray in clay color. Naturally occurring hematite will present light to medium “reddish” in color, with no goldish hue. Iron disulfide typically has a gold cast because the iron is oxidizing (rust), whereas hematite is not subject to this natural process.
The middle layer is dark brown ball clay which typically indicates the presence of inorganic sulfides from lignite coal particles. Lighter brown color means less inorganic material, and darker brown means more. The exception to that rule is organic particles (humus). If your sample was taken from a heavily vegetated area; then the level of organic (humus) will be higher, which like wise will create a dark brown appearance. How can you tell if its organic or inorganic? First, the collection site: open fields or valleys will have less organic material, and heavily vegetated areas will have more. Secondly, a very simple test: take a small 1/4 cup powdered clay sample and add a a bit of water at a time until it forms a pliable ball. Does not have to be all nice and neat; just pliable. If it is sticky or gummy feeling; organics. If you can roll it between your hands without it sticking or smearing; it is inorganic. Yes, there are exceptions were a sample can have both inorganic and organic materials.
Besides the obvious large particles of shale; did you notice the smaller nodules? There seems to be a heavy population of them in this sample; which means the middle layer has a higher percentage of 20-60 mesh particles. Bad thing? No, it can be used for non-functional, large format pieces. If you are going to make cups and bowls, then these larger particles have to come out. Wet processing will allow the large particles to settle out quickly, or dry processing will require a 60-80 mesh screen. This sample was found in an open eroded ditch in a field, so the color is most likely from inorganic sulfide. The presence of these sulfides also indicates a coal seam is nearby: which I happen to know is correct because of the numerous coal mines located locally back in the late 1800’s. This knowledge also helps determine the plasticity of ball clay located next to coal seams; typically they are more plastic. 
The bottom (thin layer) is free from large particles, and because this is a sedimentary sample; also means it is finer and more plastic. As with all clay sediments; larger particles drop out first, and smaller particles drop out last. Remember, this sample was photographed upside down to capture color variance. So the thin layer on the bottom, is actually the top of the sample. Can you field test plasticity? yes. Make a 1/4 cup of the middle layer, and a 1/4 cup of the bottom layer to start. If you have a scale, you can accurately measure what you add to each sample to create a pliable ball. If no scale; add 1 teaspoon, add a second, and once it begins to form a ball, then add 1/2 teaspoon until it becomes a pliable ball that does not crumble, nor overly wet and sticky. Low plasticity clay requires less water to form a pliable ball, and a high plasticity clay requires more water for the same. Exact? no- but will give you some general sense and direction.
Tom
 

You can run 20 amps through a 13 amp (British Standard 1362) fuse without it blowing out. My Cromartie HobbyTech 40 litre draws about 2.9kw/12 amps through a 13 amp plug fuse without any problems or excessive heat generation. For a 2.5kw kiln I would still change from parallel elements (46 ohms per element) to series (11.5 ohms per element) as they will use a thicker wire giving better element life. I know Cromartie advise that on all their 40 litre kilns and it seems sensible to do it here too.

You can run up to 3kw through a 13 amp fuse no problem. 
 
Those elements are wired in parallel so you need to use 1/RTotal = 1/R1 + 1/R2 
If I assume the bottom element has the same ohms as the top 52 ohms you measured it comes out to 26 ohms (2.2kw) for RTotal so it seems like they may have upgraded the elements to draw 2.5kw.
 
You will be better off switching from parallel to series elements as then they can use thicker wire and the elements should last longer. I do agree if you order a 2kw set they will probably be worse than what you have now.

Are you buying in the clay? I wouldn't think there's much price difference if you are making it up from raw materials?
 
I was actually doing some tests yesterday to try and get 1.8sg, it has been pretty easy to get to 1.7sg with:
1000g Dry Material : 430g Water : 3g Sodium Silicate (140s) : 0.1g Soda Ash
 
Yesterday I tried 
1000g Dry Material : 400g Water : 7g Sodium Silicate (140s) : 0.1g Soda Ash (It was 1.75sg after initial mixing but 1.8sg this morning which is a little odd. Probably a measuring error on my part)
1000g Dry Material : 375 Water : 5g Sodium Silicate  (140s): 1g Soda Ash (1.8sg after initial mixing and still 1.8sg this morning)
They are slightly more viscous than I would like and I have read that going over 0.3% Sodium Silicate is not great for mold life but they cast fine this morning and poured out easily after 20min in the mold.
 
My clay recipe is
Hymod AT Ball Clay - 60
Nepheline Syenite - 30
Petalite - 5
Alkaline Frit - 5
Not exactly stoneware as it is fired to cone04. I ran out of Neph otherwise I would do more tests. Thought about using soda feldspar instead as it should act the same with my deflocculation tests?

@Callie Beller Diesel You could write it out as:
dry weight = portion weight / total weight x batch weight
 
You could either work it out per bucket of slip or make sure to take the dry weight off the batch weight for next time you work it out. Using Callie's example ~
1500 / 7500 x 5000 = 1000 
if you wanted to keep working it out every time you need to take off the 1000 of dry weight from the batch weight for next time so it would be
1500 / 6000 x 4000 = 1000 (assuming you haven't lost water to evaporation) 
 
If the slip is thin enough to measure the volume accurately you can weigh a volume of slip and then
(volume of slip weight - same volume of water weight) x 5/3 = dry weight
 
If you can measure the specific gravity and know what dry weight you need you can also work out what volume of slip you want with
volume needed = (3 x dry weight) / ((5 x specific gravity) -5)
 

So here’s the new plug, you can see how they shaved off the cord exterior. The original plug was obviously the same color as the cord, not black. Talked to the business I bought the kiln from and they agreed the electricians had no reason to do this and should take responsibility for it. The owner of the electrician business bought me a new skutt kiln power cord and is ordering the correct receptacle and will install both on Monday. Thank you for your insights, very much appreciated!! Still can’t believe they cut my plug off lol!!

Hi High Bridge and everyone! I am back with good news! last week I did firing with the new elements we made and my kiln reached cone 6 temperature in 4.5 hr, yay...
I didn't buy 12 g wire, it was too expensive, instead, I bought 14 g, cut enough wire to make 8 ohms for each element, winded it, then stretched it to the length we needed, and installed it. Accidentally, the rod I was winding the wire on had a perfect size and fit perfectly. Later I realized that if the rod was bigger I would not be able to insert the elements in the grooves.
Changing the elements was so much simpler than I feared. I probably was reading  F.Olsen's book too much, lol. But after all the self-doubt I made my kiln work, and thank you for your support!
Elena

If you’re wanting to mix a large master batch that then gets divided out, leave out the dry mixing entirely, but weigh the water. If you know how much water went into the batch you can divide it out evenly. If you keep to metric measurements, this will be easier, because 1 ml of water weighs 1 gram. It doesn’t work like that for all fluids, but it does for water. If you are used to using a measuring cup, check how accurate it is by filling it to a given measurement line and weighing it to make sure it’s close enough for your purposes.
For instance, if you add 2500 g of water to your 5000g batch, the whole thing will weight 7500g, so a quantity of slip that weighs 1500g will contain 1000g of slip base. (Numbers made up off the top of my head for ease. You may have to play with your water additions to get your consistency right. Just record what you did.)
From there, you can add your colourants to portions of your master batch. To mix thoroughly, you will need to use a stick blender that rotates really fast. If you use something slower like a jiffy mixer, you’ll have to let it mix a lot longer to get everything distributed properly. For some colourants that don’t break up easily, you may have to sieve the mix again. 

From what I can see, these tests appear to not report false positive below 1mg / cm2 with 95% confidence. I guess we need to define “trace” amounts that would constitute not having lead.
Some info from the EPA https://www.epa.gov/lead/hazard-standards-and-clearance-levels-lead-paint-dust-and-soil-tsca-sections-402-and-403
Allowable levels of dust are fairly low with an emphasis to not aerosolize lead by heating, scraping etc…..

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.

I think in the states 1mg per cm2 for surface transfer limits so test kits are likely to detect in this range. Correlating surface transfer to absorption likely extremely difficult though. I am not aware of any amount of lead though that folks would say is fine after polluting the whole planet with low levels of the stuff. The argument at that time for a time evolved to is it is such a “tiny amount” …… See link above for an interesting accounting IMO

@High Bridge Potterymostly they’re meant for things like antique/vintage housewares and detecting lead paint. They measure anything you can dissolve with the reagent supplied. So if there’s some lead there but it doesn’t dissolve, or if it’s below a certain amount, you could get a false negative from the home kits. They’re only meant for a quick yes/ no answer.