Jump to content


  • Content Count

  • Joined

  • Last visited

Reputation Activity

  1. Like
    douglas reacted to JessicaGrayCeramics in Why is some bisque fired to cone 06 and some to 04   
    Bisque firing you work to 06 is perfectly fine whether it was meant for food use or not. The difference is Some clays become a little more solid at 04. Clays that are mid or high fire may need a slightly higher temperature to mature. However if you are using a clay meant for low fire I'm sure it would be absolutely fine that it is bisqued to 06. If you do wish to re-fire the piece to 04 before glazing the piece, just for piece of mind you can. However I do warn you that extra firings can put stresses on the wares and cause them to crack. I bisque fire to cone 04 on a regular basis with most of my work. If you take a look at the image attached you can see a lot of little protruding tabs that stick out on my work. I use a mid-fire clay and fire to cone 6 for the glaze firing. The way my work is made the tabs break off too easily at cone 06. So I have figured out that if I fire to cone 04 the strength of the tabs on my work is much greater. Bisque firing can also be done at cone 08. The cone necessary really depends on the clay body and the artists techniques. It is a personal thing depending on how you use your work. It is not necessary to bisque to 04 unless your work needs it for stability.

  2. Like
    douglas reacted to Min in cone 6 red glazes   
    Chrome tin reds just need the tiniest bit of chrome, like in the range of 0 point 2 If you are making up a 100 gram test batch you need a well calibrated scale that can accurately do tenths of a gram. Sounds like you just used too much chrome for those tests. Copper reds are fired in reduction to get red, you will get green in an electric kiln.
    Welcome to the forums 
  3. Like
    douglas reacted to oldlady in do your best in all things even when you   
    just finished spraying slip onto a large tray.  did a really dumb thing, knew better and this is the result.
    the slip was colored with cerulean mason stain.  does that mean my radio will only play the blues now???

  4. Like
    douglas got a reaction from laughlin in Underglaze wash on top of bisqued underglaze?   
    Another approach to aging the handle is to take a walk outside with some sand paper and an x-acto knife and scratch and sand away some of the under glaze.  Use fine sand paper at the end to get rid of any jagged spots. You can still add a wash to this afterwards if it needs it.
  5. Like
    douglas got a reaction from Chilly in Choosing a clay for slip casting big pot   
    Since you are making the original model out of wood, you might be better off using a hump mold and slabs vs. trying to master slip casting. I know you are not proficient in clay, but using a slab and hump mold is pretty easy even for beginners. There are plenty of youtube tutorials you can watch, but here is a quick read to get the idea. 
    This way you are only paying for clay, glaze, and firing fees. You would probably need to use several large slabs since rolling a huge slab like that might be difficult. 

  6. Like
    douglas reacted to glazenerd in Why did my plates split ?   
    What concerns me is the width of these cracks, as well as the uniformity on all three pieces. Not hairline, nor S cracks, but rather large (as clay goes). Measure the width next time after you throw: and measure at bone dry: compare. I would expect to see shrinkage in the 10% range. The crack pattern indicates drag to me: which is why I think Min is correct.
    Given the shape; you essentially have the same surface contact as tile. So here is a tile trick that will solve the drag issue. Go to the Dollar Store and get the cheapest and thinnest roll of wax paper you can find. Cut into pieces slightly larger than your plates, and lay the thrown pieces on them after you cut them from the wheel. (when they can be handled safely) Then as they shrink, the wax paper will move with them.  Old tile trick.... which should work for you. Might need very minor touch up on the bottom when bone dry.
    Side note: suspect Nep SY was used as the body flux: which rapidly accelerates drying of stoneware. How long after they were thrown, did the rims dry? (guessing fast)
  7. Like
    douglas reacted to bciskepottery in pieces warping during glaze firing   
    Does your yarn bowl design include a cut in the rim to allow threading the yarn? If so, that might be contributing to the rim distortion . . . as the clay expands and shrinks during glaze firing, the cut in the rim may be allowing it to distort. Because your bisque temperature is lower, it does not occur at that firing, only when you hit the higher temperatures of a glaze fire. You might think about altering your design, perhaps foregoing the cut in the rim for just a hole in the side that allows the yarn to come through. Or, you could switch to glazing at low fire temperatures.
    As for the platters, in general, make sure you are compressing the slabs, rolling them in all directions . . . especially if you are using a slab roller to make them. Also, after rolling, take the ware board with slab on it and drop it flat against the floor from about mid-waist high -- that will compress the slab. Handle slabs minimally to prevent warping. If you could tell how you make your slabs, it might be easier to diagnose what is going wrong.
  8. Like
    douglas reacted to curt in Chicken Scratch   
    Depends on the chemistry of your granite but most granites I have met are pretty well behaved.  I have melted some and it does not really pop or even spit much.  Problem is more that it won’t really melt all that well.  Kind of like small chunks with rounded-off edges.
  9. Like
    douglas reacted to Magnolia Mud Research in Chicken Scratch   
    Take a small spoonfool of the scratch and place it in a  test cup in your next gas reduction cone 10 firing;  see what happens to the crushed granite.  Choose a spot for you 'test' in the  gas fired kiln to be as representative of a wood kiln environment as you can get -- like hot and/or heavy reduction.
    I expect some chunks will  will just lay there and some will start to melt. LT
  10. Like
    douglas got a reaction from Textree in Choosing a clay for slip casting big pot   
    Since you are making the original model out of wood, you might be better off using a hump mold and slabs vs. trying to master slip casting. I know you are not proficient in clay, but using a slab and hump mold is pretty easy even for beginners. There are plenty of youtube tutorials you can watch, but here is a quick read to get the idea. 
    This way you are only paying for clay, glaze, and firing fees. You would probably need to use several large slabs since rolling a huge slab like that might be difficult. 

  11. Like
    douglas reacted to Min in Glasslike Crystals in Wet Glaze - What the...?   
    You can supply the lithium from a frit to (mostly) avoid getting the crystals if they get to be a nuisance. I played with your recipe over lunch, reduced the custer by over half to get some clay in the recipe, could leave the talc out altogether as it’s not going to be doing much. Sodium and potassium amounts are more or less reversed, supplied mostly from the custer and 3110. Other fluxes remain the same, as does the alumina and silica. Should behave better in the bucket and application, probably wouldn’t need to add bentonite. Expansion is tiny bit lower but still really high as it is in your recipe. (your recipe is glaze #1, my version of it is #2)

  12. Like
    douglas reacted to Joseph Fireborn in Throwing Studio on 2nd Floor house?   
    If the room has HVAC return you need to consider that in the equation. If I was doing something like this. I would wipe down the surfaces and floor after every single session to avoid clay dust circulating through my entire house. I don't know how good of a filter your HVAC system has, but most people use pretty crappy filters and have dated HVAC systems, so if you're in this category consider maybe closing the return if your HVAC system will be okay with that. Some can handle closing off returns and others screw with the system. 
    I don't know what type of garage you have, but it might be easier to insulate your garage then make all the changes for this room. Hauling pots up and down stairs is going to be a challenge, even bone dry pots can get heavy carrying full ware boards downstairs. I agree with Min that you need some type of flooring that you can mop. It doesn't matter how clean you try to be, clay is just naturally messy. I throw pretty dry and trim slowly, and I still make a darn mess.
    I had a  room on the same floor as my garage that wasn't being used and I decided it would be easier to just insulate my garage door and work in the 40-degree temps in the winter. I don't know how cold your garage gets, but you could get wall panel heaters and put them on timers to start an hour or two before you go in there so it is nice and toasty. 
    This isn't to dampen your dreams. You could easily make that room work, we are just telling you the downsides and the things you need to consider. It is up to you to decide how clean of a person you are going to be with the dust. I have seen studios that are horrendous and some that are sparkling clean.
    Good luck and let us know what you end up doing and show us pics of the final room!
  13. Like
    douglas reacted to Min in Throwing Studio on 2nd Floor house?   
    I'ld take that foam flooring out all together and put down some sheet flooring that you can wet mop. Have a pair of shoes that stay in your workroom so you don't track dust through the house. Also, if you can use that ceiling fan somewhere else in your house I'ld take it out since you're not going to want to have it blowing dust around. 
  14. Like
    douglas reacted to Min in Fill In already fired logo in bowls   
    Fish Sauce Slip can be made really quite thick and works on greenware and bisque, I would try that on one that has not been glazed yet to fill it in.
    Fish Sauce Recipe ^04 - 10
    Kona F4 23.5% (Minspar)
    Grolleg 43.6%
    Pyrophyllite 7.8%
    Bentonite 9.5% ( I use 5 macaloid / bentone MA)
    Silica 15.6%
    Welcome to the forums 
  15. Like
    douglas reacted to hitchmss in Seeing is believing   
    Water reaches its boiling point at 212 F. Teach your students the stages of firing and what occurs. Like Neil said, any moisture still present expands rapidly.  Go through water smoking stage slowly and evap all that moisture off and you're good to go. I've single fired work that was glazed and fired in the same day (glazed, loaded immediately and began firing). Go slowly through that first stage though. You can show your kids evidence of moisture that is still present in even bone dry work by holding a mason jar loosely over a spy hole at the early stages of firing (100-200 deg), or using a mirror held over the spy hole. Moisture will condensate on the glass surface. Good way to check if you've dried your work out long enough before ramping up too!
  16. Like
    douglas got a reaction from yappystudent in It's my own fault I know_just a wee rant   
    You should probably bail.

    However it also sounds like there are customers, and people willing to volunteer. So maybe if the owner is losing money, it is because of their incompetence and not that the location and market are a losing proposition. 
    Maybe if you and the other volunteers group together you can offer to take the business to a non-profit status. If they are losing money every month, and the equipment is as bad as it sounds, they would probably do better walking away from the rent payment than hang on a few more months before shutting the doors. 
  17. Like
    douglas reacted to Min in Chicken Scratch   
    Calcium based chicken scratch is going to behave as seashells do in the firing which is not going to behave at all like the granite based chicken scratch. Article from Rimas VisGirda here, he discusses using granite, decomposed granite and other inclusions he uses. 
  18. Like
    douglas reacted to andros in Glaze issue   
    Finally I've done it!
    I have applied a couple of your suggestions: thinner glaze layers, no sanding, clean with water and soap (not only water) and work with gloves. And finally I've succeeded in obtain a decent result! (neglect the one on left-bottom, it's a failed test with underglazes...)
    Thank you again for your suggestions!

  19. Like
    douglas reacted to Mark C. in Plaster Vs. Bisque Bats And Molds   
    I use homemade plaster bats in my production-10 tons a year of porcelain for many many decades with ZERO issues from plaster. I did drop one on my foot once and it hurt.
    I would not be able to make the production I do without plaster bats- they dry the bottoms out evenly and fast. The only drawback is they are a bit heavier to move on ware boards.
    The whole explosion plaster phobia is like many wives tales you hear in ceramics-like cones going bad as they are to old or air bubbles blowing up pots or glaze getting old or bad gas from the supplier. Never seen it happen in 44 years.
    Over about 15 years I had worn down some (like 40 or 50) of my smaller mug bats . They had a uneven surface so I took my wheel outside glued a 40 -60 grit rough balck sandpaper to a 12 inch wood bat and ground down all the uneven surfaces on the spinning wheel. That fixed them all perfectly flat again. They will outlast me and at least 30 -40 years of production work. If you make them as Min says they will never degrade.I have some from the 70s still in service.If you swap out clay bodes you can just wash them and dry them and bingo they are ready for whatever color clay you now work with.
    If you snap one just use waterproof wood glue and glue it up with a clamp-they will last another 20 years glued up as I have a few that I have done over that decades with glue.
    I throw a clay pad on the wheel head and stick them to that and use a tool to pop off the bats.
    Homemade Plaster bats are the best kept secret of production potters.Just like homemade music is for musicians.
  20. Like
    douglas reacted to Min in Plaster Vs. Bisque Bats And Molds   
    I can see not using them in a teaching studio but I’ve had zero problems using plaster batts for many years in my workshop. For cleaning them off I use a yellow Sherrill rib. 
    Haven’t had to replace any of mine, think clay composition and fluxes used in it will make a difference to the amount of salt fuzzies you get on them. Plus making the plaster up with the correct amount of water so they are strong. I use wood dish racks to store and dry  them out between uses. I have had no problems recycling porcelain trimmings etc. I probably shouldn’t but I use a metal turning tool to undercut and trim away excess clay after throwing and I still haven’t had any problems. 
    I made mine using No1 pottery plaster and springform cake forms, without the bottom piece, on a piece of plexiglas which made a very smooth surface. Ring of clay around the outside. Fast to make and way less expensive than buying them. I have 4 sizes from about 8†up to 16†Embroidery hoops or cutting the top of a 5 gallon bucket works too or use cake tins. 
    Not having to wire off platters is a huge plus for using plaster. What works brilliantly for me is using one of these Ziem Bat Mates on the wheel head. The plaster batts stick to it really securely, even the 16†ones don’t budge. I don’t use it like they sell it for, with plaster you don’t need pins, just the Bat Mate on the wheel head.
  21. Like
    douglas reacted to Joseph Fireborn in Plates - Slump & Hump   
    Just an update. The first of the three plates I made has popped loose form the hydro bat. I tried drying them in different sections in my greenhouse wracks. This was on the bottom with the zipper not zipped. So it got the most airflow around it. I figured I would try drying them differently to see if it made any difference in the hydro bat performance. 
    The others are still not loose. 
    I put the greenware on the bathroom counter-top and it didn't rock at all. It also seems to come lose from the hydrobat at the proper time to trim because I was able to smooth and trim the edges on the bottom slightly at nearly the perfect trimming time. Which I thought was impressive. Also the top and the bottom side seemed to be the same wetness, which made me happy. Two big thumbs up for the hydrobats. Thanks for the recommendation.
    Looking at this plate is daunting though. So much room for beautiful artwork.
    I just wanted to post this to give an update. The next one will be glazed plates.
  22. Like
    douglas reacted to Chris Campbell in Plates - Slump & Hump   
    Another idea is to throw a few hump molds.
    Load the clay on a bat and smooth it on your wheel until you get the inside shapes you want your plates to be.
    Let them set up to leather hard and use to make a few plates.
    When you are done, simply re-cycle the clay.
    I like making my molds out of clay because this process does not leave you with a whole bunch of heavy plaster molds or bulky styrofoam molds.
  23. Like
    douglas reacted to GEP in Plates - Slump & Hump   
    I make hundreds of plates on hump molds per year. Generally speaking this is easier than throwing plates. But there is a long development process for designing and making the molds, and learning how to handle slabs soundly enough to make plates that don't warp. I would plan to spend about a year on this process. You will throw away a lot of molds (when you realize the shape isn't quite right), and you will recycle a lot of plates, and hammer a lot of fired and warped plates.
    If your goal is to make a one set of plates for personal use, it would be much faster to throw them.
    I like the form in the photo you linked. To keep them as flat a possible, first make sure they are as evenly thick as possible, especially in the corner where the floor meets the wall. Compress that flat floor with a straight-edge wood rib. Compress it like crazy. Allow them to dry on a surface that is completely and reliably flat. Dry them slowly and evenly. Make sure your kiln shelves are flat and free of bumps and debris. Plan on some amount of warping anyways, so throw more than you need.
  24. Like
    douglas reacted to Mark C. in Ceramic Pincushions-Everything You Need To Know To Make Them   
    Ok maybe you never have thought about them but if you did here is how they are made or at least one way to make them.
    I used to make these and do not anymore due the fact that the market died. I made hundreds of them each year in the 70’s -80’s and 90’s. My guess is folks stopped sewing about 2001. Maybe it was a few years later. If they develop an App for sewing on the I-phone, maybe sewing will come back someday. Since I’m one the sons of a mother who taught home economics for a lifelong career I know a bit about fabric and sewing.
    This is the only pincushion I kept from 3 decades of making them. Most where glazed in solid colors. A few had these cobalt cats and some pigs and a few dogs as well as a few other animals but the lions share where solid glaze colors. All where fired to cone 10 and all porcelain? The glazes where snappy bright.
    The holes that hold the string are optional ( they work without this touch) and if you make a tool like the one shown which is laminated plastic it will make the holes space out perfectly-they now sell this tool on the market now from some supplier(MK?). I made mine before that existed in the 70's. It makes the 6-hole space very quick.Just drop in center of circle form and use a needle tool to score some light marks for the holes.
    You throw the base and let dry a tad them add the holes –I use a brass hole maker to cut the small hole in the clay when its just right moisture wise. Dry, then fire as normal.I suggest cleaning the glaze from the holes with a needle too or (small drill bit-best) before firing so they do not clog up
    The fabric is 10-to 12-inch squares-I used to but only remnants as cheap as I could fine prints and solids. I used polyester batting as the stuffing. I got mine free from a local manufacturer who used large amounts and would give me the non-perfect stuff-I got it by the truckload literally. To assemble you would cut the batting and stuff it into a piece of ladies pantyhose (I got large amounts of these at thrift shops). You would cut the legs into 3rds and stuff the batting and tie it off into a ball. These where covered with the fabric and color matched to the glazes-I use about 15 glazes not counting combos. Matching it up is an art as well.
    I use a 3.5-inch neoprene rubber bottom on them to keep them from sliding around-I bought these by the hundreds. These where a big hit especially during the holiday’s as gifts.
    Now that you know how to make them you can make a few yourself .I considered writing a piece in a magazine about these but this is easier and more direct. My last suggestion was never responded to anyway. Those editors must be a touchy bunch.
    I gave up this form over a decade ago.They still are cute and you never know somebody may still sew?
    Happy pinning

  25. Like
    douglas reacted to Marcia Selsor in Deflocculate Or Add Water?   
    Here is a simple way to determine the SP (specific gravity) of your glaze.
    I would recommend not using a deflocculant because it is difficult to undo it once added. Adding water is a much more simple remedy.
  • Create New...

Important Information

By using this site, you agree to our Terms of Use.