Bill Kielb

Yes testing is good, definitely test. As far as calculated COE and whether it will craze, I have not found any real reliability or real world parallel to the fired COE. Some folks like the calculation some do not. Definitely test, I think that’s been suggested throughout. Even if the calculated COE did not change, always test to make sure it matches your clay.

I learned as: “ Slips are predominantly liquefied clay; they usually are applied on wet to dry greenware. Engobes usually have a lower clay content and also can be used on bisque-fired ware. The word slip generally is used to describe any clay in liquid form. All slips and engobes can be colored with oxides, carbonates and stains.” Here or ceramics network.org……. Somewhere! Locally I find folks more often than not refer to engobes and use on bisque but observe it is hard to define where one stops and another starts.

The sodium decreases very slightly, prox. 0.01, magnesium increases by .prox. 0.01 and calcium decreases by 0.01. All a result of lowering the 3134. The flux ratio moves from prox 0.21:0.79 to 0.2:0.8, again a change of prox 0.01 all pretty immaterial and still in an expected durable range. so I would expect it’s still an easy way to try to work with the same recipe and reduce the gloss while not changing its durability. It may change the fit and certainly test durability but if it gets the desired look, an easy way to adjust the expected surface by following the expected gloss and also likely gets rid of the somewhat potential oversupply of boron as well. So could be a winner all around even saving on raw material. None of those numbers would be a relatively high or low change to me except the initial boron. Probably should mention, your new 100% normalized recipe to record would be epk 26.32 3134 19.74 G200 26.32 woll 19.74 talc. 7.89 otherwise just mix up a small batch as you have without silica and a 5% decrease in 3134 to try. it just won’t add up to 100%. If it works, probably record the normalized above and keep that for reference / publication. As you can see it really has the effect of raising the relative portions of epk, g200 …… slightly by omitting others. Recipes that are mysteriously whole numbers such as 20,20,20 etc… often are many times the result of convenience for the initial trials. Folks optimizing recipes rarely land on a bunch of whole numbers so this Change may simply be an improvement on an old trial and error recipe. Its hard to know by looking at the formula until you try it and of course test.

The easiest way I can think of is slowly reduce the silica and see if you can satisfy your desired level of gloss. In effect you will be changing the Si:Al ratio (lowering it). In general a ratio of 7:1 ought to be glossy and as it decreases toward 6:1, 5:1 the finish should move towards matte. Of course this can’t be done forever and may change the glaze fit but it’s likely the easiest thing to try. Unfortunately the best you can do just removing all silica is 7:1 which in theory is still glossy. The epk, 3134 and wollastonite contribute significant silica already. Finally you have about 0.19 boron, if you are firing cone 6 you really only likely need 0.15, so maybe a quick test reducing the 3134 from 20% to 15% and the silica to zero or near zero as a quick try. That gets you into the 6:1 range and might be perfect for your look. No guarantees, but pretty easy to try.

Generally layered glazes provides some properties of each glaze and are very different than mixing the glazes in advance in one uniform solution. It’s pretty unlikely in my view that a mixed result will resemble a layered result so yes, testing is the only way to know for sure in my experience.

Have you fired them to cone 6 in the past?

Test for sure, no reason not to. Cone 7/8 glazes interesting! Are they commercial and advertised as maturing at cone 7/8? If they are not commercial and simply formulas tested to cone 7/8 then it would be interesting to see the formulas. If your cone 7/8 glazes fired to cone 6 have the expected surface melt then a little durability testing could give you confidence they are good at cone 6, else firing cone six with a 15-20 minute hold could provide somewhat of a solution.

If it helps I really liked the course and the 4 months time limit was more than time to get through the lesson but I chose to finish it like any college course, watch and take notes during the lectures. Re-watch, screen shot - add to my notes as needed. Sue McLeod was a student of Katz at one time and offers similar teaching but also many free handouts. https://suemcleodceramics.com/theartofglazechemistry/ I mention because in addition to presenting glazes by composition, RT Stull plays an important part of both classes. . Sue includes Stull, so similar teaching. Stull was not super common but his work definitely adds to understanding chemistry IMO . Sues courses are more from the perspective of a studio technician I believe, so solving glaze problems that are common…… and I believe she provides a limited lifetime of access. I can say that if you finished the CMW lectures and understood them fully you are likely in a better position than just learning specific cause and effect knowledge. At the beginning of that class you should have developed a solid understanding of UMF which should prove useful for a long time.

1100 f is way below cone 6 and enameling kilns may not have been designed to make cone 6. Cone 04 - prox 1945f, cone 6 2232f. Anyway for 120v, maybe 120v infinite switch.

Unfortunately this is a fairly complex kiln. An early attempt to automate before digital controls. It did have some popularity though given how many seem to still be kicking. To solve this you likely will need solid troubleshooting skills. Some of your symptoms cause and effect are described throughout the thread. The two special timers used in this design (bottom of schematic) tend to go bad after awhile and are not readily economically replaceable. That it does not shut off when switched to off may indicate the infinite switch does not function, especially if the pilot light does not turn off. My best thought: if testing relays is not in your wheelhouse then maybe If you can find a good kiln tech, this is one that may be worth every penny to have it diagnosed. In fact the tech may suggest removing much of the complexity of this thing and installing two simple infinite switches in place of the relays and timers.

Epoxy made by a reputable firm is structural and fills voids so that is common in my experience.

Hey just a late add here, you will be looking to protect your eyes from infrared light, not necessarily ultra violet. The lowest shading coefficient I have seen is 3 with a range of 3 to 6. If you buy reputable welding goggles or even buy from a reputable kiln supply house then this should not be an issue. I have on occasion met folks who bought UV glasses, more sunglasses however so worth mentioning that you take care and purchase proper lenses. For kilns you will be looking into an extreme infrared environment.

Cones are easy, If you want to follow the cone chart then for your last segment go 60c/hr in the last 100c of the firing to 1222c. So pick a cone, let’s say 6. find the temperature in the 60c per hour column = 1222 subtract 100 from it, 1222-100 =1122 program your final segment to start at 1122, go 60c per hour and end at 1222. the last 100c is super important to the heatwork done. From the times you state though it does not appear your kiln is keeping up with the program and therefore likely worn elements. For a worn kiln you may be able to use the 15c column which means for cone 6, your ending temperature is 1185c, final segment is 1085c => 1185c and final segment firing speed is 15c per hour. There is a limit to how slow you can go and how glazes perform. As far as cones and many other things, In the final segment It’s rarely only about top temperature. As an example, just like baking something, it’s not simply 170c, it’s 170c for 30 minutes ………. For kilns we depend on rate per hour though. If you cannot find elements Euclids.com can likely wind new and they ship worldwide.

Just a note, the separation thickness definitely has a major impact on holding power. A friend - very accomplished potter - has been rehabbing both arms after major surgery and needed to resort to trial and error for her throwing thickness. As part of rehab she has been making small pots / bud vases over time to rehab …… lots of them thus far, so speed and ease in glazing led her to the magnets. Separation between the magnets has a giant effect that likely requires testing to figure out.

Cress is still in business so manuals and wiring diagrams available. Knowing the nameplate data and operating voltage would be helpful as this kiln appears to have been made in 208v and 240 v models. https://www.cressmfg.com/resources/ hope that helps.

Yes definitely possible. So silica and alumina do not melt basically on their own below about 1600c/3000f. So they need flux to help melt at a lower temperature The fluxed reaction pretty much takes place in the last 100c of the firing, prior there is just not enough energy to get things going. So temperature and firing speed in the last 100c is super critical, to which PeterH has posted the Orton cone chart above. As kiln elements age their power decreases and eventually they can’t make a reasonable final firing speed and things begin to over fire. The same goes for anything that slows down the firing such as worn elements AND a cold external firing temperature. In the end though -9c is cold but not that cold so likely the elements are fairly worn. How many firings are on them and to what cone do you routinely fire?

If I was recreating that I think I would paint the blue with underglaze including the wash effect then overglaze with a matte clear. Likely a glossy clear or decent liner for the interior and matte for the exterior, since they are all functional. if I was dead set on matte everywhere, inside and out then I would try and make sure the interior was more satin, not as prone to metal marking and reasonably known to be durable. So to me, the underglaze and artwork would be a yes and the matte clear would be a matter of if you could find a matte you like. If this was sculpture and non functional then I could just underfire the commercial matte to make it more matte and see if I could find a temperature best look combination. If I were mixing my own glazes (cone 5/6) then I would just dial in the amount of matte / gloss I wanted by varying the silica in the recipe until I got the level I wanted. Here is a recipe formulated very dry or matte and will go to full gloss as more silica is added. You are welcome to try, this is not for everyone though. Some folks love it and for others, not so much. https://glazy.org/recipes/19734

The short answer is to fire the ware to planned cone but use a slow or bisque type schedule. Not all clay / glazes work for single fire so experimenting or testing is super important.

Without going into many paragraphs, all those firing techniques have characteristic looks with traditional wood being the hottest and likely the most random to let’s say cone 12 ish. Gas and electric are just different types of fuels, but gas traditionally would go to cone 10 and is also ideal for reduction where a handful of oxides are affected by a carbon monoxide rich atmosphere which causes variation in color and influence some oxides to be less refractory than in oxidation. Electric is mostly reserved for cone 6 and below and can be associated with brighter colors, less energy use …. Cone 6 oxidation electric is probably most popular for studios and hobby. Of course there are exceptions to all the above.I think the best way to begin to understand is to know the typical cone and look at as many pieces of each as you can fired with different fuels. This will give you an idea of the look and typical temperature, clay and glazes required. That IMO would be a good start, but as with most things in ceramics one can spend a lifetime learning the firing skills, glazing techniques, throwing techniques etc…. To provide a desired artistic look. For a start learn the look in common with each technique then if interested, learn the materials and process.

Those are pretty close cone wise but a tad over fired or strong cone 6 so you could tweak slightly with offsets. My guess is your glaze is happier at cone 5. Glaze firings generally can go fast. Since the ware is dewatered and all the organics have been removed many find their glazes work just fine with medium or fast firing. Having said that slow bisque is more popular to remove all organics. Darker clays generally slower than light. Since you have so many pin holes there could be several causes originating with how well was the clay bisqued, how evenly was the glaze applied, is it really a cone 5 glaze. From the picture, it looks over fired, so to start properly bisqued test tiles, one two three coats of glaze etc…. Fire to different cones. For problematic or fussy glazes and clay body combinations they can be dealt with a drop and hold schedule or other methods as appropriate. First thing IMO is get all the prep stuff right and test (using test tiles) to then see what is the best way to fire that clay and glaze. I believe that is a commercial glaze and some of my very first pieces used it in layers to get the look. Temperature sensitive, base glaze sensitive and thickness sensitive from my recollection if it is the same that I used. These inconsistencies drove me to learn as much about glaze as I could find time for…… so I could just mix my own.

I just happened to look in the latest manual. The math, code requirements, and current Skutt manual seem to all agree so not sure what any distributor is saying but could be an error or a result of previously using lower system volts. Older manuals seem to show it as #8. I guess the lesson is always double check the math, pick an appropriate breaker and pick the wire. The more heating in the wire, the less heating in the kiln. Bigger is usually better for the kiln owner. If you are using roamex then the wire size will likely be larger. The adjacent conductors in a confined space tend to heat more and are derated from free space. The rule about breakers is all about reducing the heating on the breaker so it remains dependable. Heating in wires and devices is not really good.

I think it is a tweener. The Skutt manual I saw listed # 6 wire, no breaker. Sizing this not less than 125% and not more than 150%. 33.4 amps X 150% = 50.1 amp. So not more than 50.1 amps and not less than 41.75 amps (125%). One is left with choosing a 45 or 50 amp breaker each fit the rule. The Skutt kiln sizing in the manual seems fine.

Bricks do stay intact but an extremely interesting question. Lead at one time was used as a flux, no longer. One of the insidious issues with lead is it gets absorbed or transported to everything. You could do a couple lead swabs on the bricks just to check. An automatic shut off device would be great as far as operating. This kiln may have a kiln sitter. Lots to learn for sure, understanding more about clay and what temperature you will be working in will become super important as to whether this will work for you. Post a picture or two, inside and out. This kiln is old enough so probably good to let folks here see it to provide more informed precautions. As far as an interesting story of potentially how to pollute an entire planet with lead google Thomas Midgley.

That kiln is basically my age and I inspect everything when I wake up just to be sure it all works. Just kidding, I would inspect all the electrical and make sure everything is safe and in order. Hook to a properly sized circuit breaker with properly sized wire should be fine to try. Are you planning on firing to a specific cone, will this be for firing your work or is this something you would like to be sure functions prior to sale?

I would search white and cone 6 for temperature then look at the pictures https://glazy.org/search?keywords=White&base_type=460&cone=30&photo=false&production=false Here is one with movement https://glazy.org/recipes/3019 and another …. might need more color though https://glazy.org/recipes/3022 and a third https://glazy.org/recipes/195539 Drippy movement https://glazy.org/recipes/175463 (Low Alumina) Less movement https://glazy.org/recipes/3136 Look for similarities, those with lower alumina generally will move more than high so something in the 0.3 range is much more likely to move than something in the 0.5 range.