perkolator got a reaction from RichN in Adding A Frit To An Oxide To Create An Oxide Wash
You can use either Frit, Gerstley Borate, or make an underglaze with equal parts clay color and flux. Frits, being fired material usually leave a gritty/sandy texture to the wash, some people use CMC, laundry starch, karo syrup, etc to help. Usually I use GB and CMC gum solution, sometimes add a little bit of EPK in it too.
Look up Linda Arbuckle's majolica notes, she's got a lot of suggestions for combos of washes. Most are by volume, not weight.
Here ya go:
perkolator got a reaction from Babs in Newspaper burnout in clay busts...help!
Main reason why I discourage people from using wadded newspaper and other armatures when hand building sculpture, they're usually unnecessary with proper construction methods and can create problems like you're experiencing.
I'd bust out a drill and make a hole up into the neck cavity from the base, then get at it with extracting as much paper as you can.
perkolator got a reaction from Crunchypop in Cooking Pizza In A Pottery Kiln, Toxicity ?
Like this? This round was pizza bagels but concept is the same.
I would NOT recommend this in a top-loading electric kiln, way too dangerous IMO.
Heat up to around 900*, pizzas cook in just a few minutes like a wood pizza oven. Use clay pizza stones or a brand new kiln shelf w/o wash, definitely use heat resistant PPE. After the first time I singed my eyebrows getting too close I decided it was time to make a pizza peel, WAY safer
I wouldn't worry about any toxicity unless you exclusively cook all your meals in your kiln. We all likely breathe more harmful stuff just walking through the clay studio with a dirty floor, breathing in a big city, walking past an idling car in a parking lot, sitting in traffic, etc.
perkolator got a reaction from D.M.Ernst in Glazes that don't require heat/kiln firing?
I can't think of anything either that resembles glaze and is a cold surface other than paint. Closest thing I could suggest is silicone ( and possibly clear epoxy resin)
There are silicone casting products that are rated food-safe - an example would be Smooth-On "SORTA-Clear", which is a translucent silicone rubber (I think you can tint/color it too?)
Not sure about the epoxy resin products. I'd assume fine for cold items, but not for warm items. Silicone is good up to at least 400+*F, you can stick it in the oven for baking or pour molten sugar in them for candy, etc.
perkolator got a reaction from Roberta12 in Food Coloring - dying glazes for better application.
I sometimes use food coloring in my glazes - because I'm colorblind and many raw glazes look identical to me. Doesn't matter which brand you use, they will all make color and burn out in the firing, i've been using McCormack from grocery store.
I first started doing it when I was spraying glaze - I'd put a drop or two into my sprayer pot, spray it on and change the color enough to see each layer.
perkolator got a reaction from Magnolia Mud Research in Getting High Magnesium Glazes To Stick On Vertical Surfaces.
Our students use crawl glazes on vertical surfaces all the time. The work is lifesize and being made by 18-20-something year old undergrads with no prior ceramics experience...and usually once-fired to ^04
I've noticed the key to getting crawl glazes to stick is to water it down and build up the surface in layers...or spray it on. We definitely use CMC gum, which helps as a binder, and trying to not mix the glaze too far in advance seems to help too.
The students have found many crawl recipes over the years but for the most part they're using: SDSU crawl, LW Lichen, 3rd Degree Burn and whatever experiments they choose to do.
perkolator got a reaction from ppony123 in Making colored slip
pretty much any white slip recipe can be made into a colored slip. for most natural oxides you will use the same percentages you would in glaze recipe (so like 2% for cobalt carb = blue) if using a mason stain, you'll want to be up near 10%. my go-to basic white slip recipe is equal parts (25/25/25/25) of EPK, OM#4, Silica, and Custer Feld. you can easily tweak this recipe with flocculants/deflocculants or suspension agents to get the consistency you desire. this slip can be used at pretty much any temp range.
for a raised slip/heavy surface texture, i prefer "Arnie's Fish Sauce" and i believe it's a midrange/stoneware recipe. Mix it THICK, like yogurt or even cream cheese. this can also be colored.
23.4 F-4/Minspar/soda spar
perkolator got a reaction from cc's clases de clay in Glaze Dripped Onto Kiln Floor
I like to use a dental pick or a needle tool for glaze drips on soft brick. Weaken the surrounding brick as close to the glaze as possible, with pokes/perforations, then apply leverage and dig/pop it out. Usually this minimizes damaging the non-affected brick. For fill, use kiln mortar with about 60% brick dust mixed in - helps lessen cracking from the dissimilar COE of the brick vs mortar. Another good reference for brick repairs are the videos on Youtube from L&L Kilns.
perkolator got a reaction from D Walsh in Mason Color Vs Us Pigment?
Between these two companies that make stains -- are they comparable/interchangeable? I have always ordered Mason Color stains because that's what my local suppliers stock. I knew US Pigment existed but I never ordered from them or really looked into their product until now.
Need to order stains and after looking at price comparison I'm seeing the US Pigment stains are significantly less expensive, some of them at 1/2 price and now I'm wondering why?
Mason Color Canary Yellow #6410 = ~$29/lb.......US Pigments Canary Yellow #6410 = $15/lb
Mason Color Dark Red #6021 = ~$53/lb...............US Pigments Dark Red #6021 = $29/lb
The code/# for the stains and names are exactly the same, so I'm wondering how interchangeable they are between companies? Any reason to stick with Mason Color?
perkolator got a reaction from Chilly in Need Pictures Of Kiln With Pottery Fired Too Hot In It
I used to have a really good one from our studio but can't find it anymore. It was from a project we did once where we got a whole bunch of "unsellable" dishes from a thrift store and re-glazed them with underglazes. I think one of them was actually not clay and may have been glass -- oops
Anyways, I would personally fire it - I would just make sure it goes on either a waste shelf or inside a pre-fired firing tray/saggar to catch any mishaps.
Here's a few good ones I found on Google images:
perkolator got a reaction from Pres in Cracked Kiln Shelf
What he's doing is "staggering" the height of bowl rims, since they're all the same general height - so he can place them closer together and fit more per shelf - very smart way to load. People who are good at Tetris and puzzles excel at kiln loading!
The other method you got confused with actually used to be common in ceramics. Example: saggar fired ceramics used to be common when you had "dirty fuel" sources to fire your kiln. Inside these saggars it was common to stack/cradle glazed bowls inside one another, to maximize your volume. Since glaze obviously sticks to anything it touches, they would space the bowls apart with 3 small balls of wadding/clay to separate them - the balls would be under the clean foot ring of the top piece and they would clean a circle of glaze where it touched the inside of the bowl underneath - this way nothing sticks to glaze, its all clay-on-clay. So if you see old Chinese ceramic bowls with 3 unglazed dots in the center, it was likely fired this way and very old.
perkolator got a reaction from Stephen in Brick Repair
there's a few youtube videos regarding how to replace the bricks, it's not that hard, just time consuming. Nice thing is the Skuutt 818 isn't a very big kiln, so it's easier to manhandle the sections so you can DIY.
Basically you unplug, take the control box off then unstack the sections to get to the bottom one. Flip it over onto a flat surface and release the steel jacket. After you replace the bricks, you'll need to sand them down so everything is flat. Replace your element, then reinstall everything back together. Test fire.
You may consider getting some backup parts for your kiln if you have the $ - extra thermocouple, relay, element.
perkolator got a reaction from Phoebe3 in Imco Mid-Fire Clay Reviews Wanted
Have you called them yet and talked with Aaron?
I've used many of the IMCO pugged clays over the years, I have no complaints. Mainly we make our own clay from dry materials (which I get many from IMCO), but many of our students, local schools, local artists, etc buy their clay and seem to like it. Heck, I was over there one day and saw a pallets of Leslie Ceramics clay bodies, so I guess they're the one who produces some of Toki's pugged clays.
I have not used the Starry Night, I think that's a newer clay body of theirs? I have a 50lb bag of that ilmenite they put in it, I got it from IMCO to test out as a potential grog substitute/filler material.
My MIL used to teach HS ceramics in Sacramento and she used IMCO clays most of the time vs Laguna or other brand clay from Alpha, since IMCO delivers and Alpha doesn't. They fired to ^6, with commercial glazes and I didn't really see any issues with vitrification. From their IMCO stash I've used over the years: navajo wheel, great white, 50/50 mix, and sculpture 50, IMCO sculpture mix, Elf White, Stoneware #5 and Sculpture 412.
perkolator got a reaction from Min in Building A Hydraulic Extruder
I agree to buy individual parts and custom fabricate the unit. We have a large 14" hydraulic extruder in our studio that is a one-off piece of equipment. If I recall correct, it was built by someone at Univ. of Minnesota.
Ours accepts a 16" square die plate, with an approx 14" extrusion limit. It has a hydraulic cylinder for the main ram, which as control valves for the hydraulic pressure and up/down stroke. I can stop it during mid-stroke, I can also change the speed during mid-stroke...it also tilts into horizontal position AND has a 2nd ram hidden inside the base to make it taller for extruding longer forms in vertical orientation. I can try to take some pics, but in my honest opinion this thing has some major design flaws that I would definitely change if I were to build one myself (the issues mainly are due to the capability of going into horizontal position and being able to change vertical height - it just needs some major improvements for safety). We have the Bailey pneumatic as well, I would likely share some of those design concepts if/when I finally decide to chop into this thing.
The original dies we got with our extruder were mainly for extruding slabs/tiles, but we've since made many of our own. The problem with this is that when you have a LOT of hydraulic pressure + a large diameter die plate, you can very easily snap dies in half (depending on the shape, since certain shapes restrict too much clay and create too much pressure behind it). Many of the dies with smaller apertures have to be double thick matieral (3/4" plywood) or made of something else, like steel.
perkolator got a reaction from Min in Silicone Caulking Cure Time?
Silicone generally takes around 24hrs to cure. It cures with humidity in the air, so I suppose if it's in a humid environment, possibly with heat and airflow it will cure faster.
I like E-6000, it generally takes 24hrs, but sometimes takes longer. These I'd go 72hrs if you had the time available.
I usually prefer a 2-part epoxy though. Not too much a fan of the quicker 5min stuff, the longer the cure and the more opaque, the stronger it is. If it doesn't have to be a clear, PC-11 (white) and PC-7 (charcoal) are my preferred "strong" paste epoxy. I believe the PC epoxy is stronger than JB weld, but JB beats it in thermal resistance. I can only find it on the shelf of Ace Hardware; or online. Don't really have a preferred clear 2-part epoxy yet, but I'd go 30-min cure.
perkolator got a reaction from Amreyes1 in Technical Requirements Skutt Kiln
I just went through this with our 714 -- it takes a 20A dedicated circuit.
Was having issues with out smaller 609 (turned out to be a bad receptacle) and had an electrician in studio to inspect power on both our 120v test kilns. I was questioning the 20A circuit for the 709 since its amperage rating is too close and if we managed to fry a less amp kiln's wiring, what about the one drawing more juice. Both Skutt and the electrician confirmed 20A was the common setup on both models since a 25A circuit is only possible at the breaker side, there are no 25A receptacles and the kiln would have to be hard-wired to a shutoff for this to work. I need to be able to unplug the kiln for stuff like element and brick repairs after someone blows up their test tiles in these powerful little kilns - so I chose to just switch to dedicated 20A twist-loc receptacles and plugs for ease of service. The other way suggested by the electrician was to possibly setup the kiln with 30A and install a lower amperage inline fuse on the control box.
perkolator got a reaction from eoteceramics in Silica Sand For Use Under Slabs
12"x12" isn't that big of a slab. dunno what firing schedule you're using but likely it's too fast.
slabs and similar work with large flat surface areas against a shelf (like slabs, and big platters/pots without a foot trimmed into it) tend to have two main issues with firing.
-One is that they are a big surface area, sitting flat against a shelf, thus the heat cannot easily penetrate to the bottom, center, of the clay. Because it was cooler than everywhere else during the time you were candling your kiln, by the time you go to your next stage of firing, this cool section kinda rapidly heats up and thus you get blow-outs. Raising/elevating the piece will help tremendously. Also slow down your firing to compensate for lack of heat penetration. Kinda the same concept if you were to stack a really tight, low height shelf in the bottom of your kiln - the heat can't penetrate very well.
-Second issue is more likely with larger work than the scale we're talking about, and the problem is usually cracking due to the friction and drag caused by the physical weight of the mass as it's trying to expand/contract in the kiln. Something under the piece
Yes, silica sand can work if you need to sit it flat. Grog will also do the same thing. Putting a layer under your piece will act as ball bearings and facilitate the movement as the clay expands/contracts. Since it's not a solid, it will also allow moisture and heat to pass through the interstices and make its way to/from the bottom. Another alternative is raising the piece on pieces of broken kiln shelf or clay pucks. Most of the time with big work, I use either the broken shelf bits or balls of kiln wadding (1/3 each: grog, silica, clay) - they do the same thing, but they have one main factor that makes me go toward them before loose sand/grog......Grog/sand can fall through the shelf crack/joint to the work below, the wadding stays put. Another benefit to the wadding and sand is that they will self-level out which is great if your kiln shelves aren't perfectly flat, but your piece was built on a flat surface.
Yes, slabs fired at an angle on their side can definitely warp. Depends on how thick/thin, how heavy, how big, the temp you're firing to, etc etc.
I lean stuff on soft brick all the time as long as there's no glaze.
perkolator got a reaction from terrim8 in Quartz Inversion
Well yes, the more mass in the form, the more they are susceptible to the forces of nature/physics/kiln firing/etc. Hard to give specifics since it varies so much depending on what it is, how it was made, etc etc.
As for quartz inversion - 2% expansion doesn't seem like much to a little cup or plate, but to a 6ft tall sculpture with a 1" thick wall will definitely have some concern and you may have to make some big changes to accommodate making that item. With bigger work it's inevitably going to be "moving more" as things shrink especially. You actually have to engineer your sculpture to accommodate certain shapes, kiln firings, etc etc.
For example, everything made from clay will shrink to some degree and obviously clay can be heavy. You may not be able to perceive the shrinkage from your average cup/mug, but if you scaled it up to a 24-36" diameter vessel you're definitely going to be able to see the shrinkage as it will be obvious at this scale. Big heavy sculpture often gets vertical cracks originating from the foot, likely due to the heavy weight of the form and the friction on the work-surface as the piece dries, this continues as it fires and shrinks again. Big work makes "walls" in the kiln that make heating uneven sometimes, so how you stack your kiln will likely effect the work too. Example of that might be firing several long-necked forms - if you cannot place these centered in relation to the heat source, it's likely the uneven heating will warp the piece and it will lean toward the heat source since that side shrinks more.
If you fire very conservatively your chances of surviving these forces are much much higher. Obviously you won't be able to fire big stuff on a fast kiln firing schedule, sometimes you even have to down-fire your work so it doesn't get dunting cracks. Keep in mind that my studio operates outside the box of your typical ceramics studio. Most of our work is fired earthenware temp, with a forgiving stoneware clay body...oh yeah and did I mention most of our stuff is once-fired?! Most of my gas kiln firings with big stuff takes about 1 week turnaround for firing - 1-3 day drying/pre-heat, up to 24hrs to fire, 2-3 days to cool. Go slow from pre-heat to quart inversion. Remember, it's not only quartz inversion to be concerned with...all ceramics still have chemical water that needs to come out too...so if you go too fast with a 1" thick piece of clay...boom....
perkolator got a reaction from porcelainbyAntoinette in Studio Safety
Silica dust is carcinogenic, try to avoid breathing any clay or glaze materials particulates whenever possible.
Some things that come to mind for general studio safety:
- Cheap disposable or reusable chemical gloves for glaze handling and misc hand-protection needs.
- Chem goggles/eye protection for cleaning out glaze containers or flying debris from chipping/grinding fired glaze.
- CMC gum in glazes to keep glaze from powdering off when transferring glazed work to kiln.
- Particulate-rated NIOSH respirator for general studio use. I like 3M N95 8210 particulate respirator. Use 8011s if you have a small face. You can get higher filtering, but they are hard to breath through IMO.
- Leather gloves for handling hot wares from kiln, sharp edges of wares stuck to kiln shelves, etc.
- Try NOT to dry sweep, use wet-cleanup methods whenever practical. Sponge it down, mop it.
- If dry sweeping use a respirator, provide ventilation, use floor sweeping compound if you have it.
- Obtain MSDS info on any chemicals you have in your studio and ACTUALLY READ IT so you know how to handle, transport or dispose of your material, etc.
- Clean up studio daily.
In regards to your mold issue, I dunno what to do there. Sounds like your studio is too well sealed. You may consider some sort of ventilation for the room. Also, I don't know how you store your wet clay or wet in-progress work, but try to isolate it with plastic or store it somehow so the moisture doesn't raise the whole room's humidity.