marshadohr Posted October 14, 2014 Report Share Posted October 14, 2014 I have had this happen twice - once on a vase I built and once on a vase thrown by a local potter of note: a white, sand-like residue appears on the outside of a vase after filling it with water and putting flowers in it. The one I made was either half and half or little loafers clay. I fired at cone 6 after bisque firiing at 06. What makes this occur? Am I under-firing my clay or is there another problem? Link to comment Share on other sites More sharing options...
bciskepottery Posted October 14, 2014 Report Share Posted October 14, 2014 If the clay body was Half and Half from Highwater, then you underfired at cone 6; at cone 6, Half and Half has a 5% absorption rate; at cone 10, less than 1%. At cone 6, you'd likely see serious seepage or weeping as the clay is not vitrified. Little Loafers is a cone 6 clay body and vitrifies at that temperature. Are you just glazing the inside or both the inside and outside? Link to comment Share on other sites More sharing options...
neilestrick Posted October 14, 2014 Report Share Posted October 14, 2014 I would expect to see the weeping on the foot if it was only a clay problem. There's something going on with the glaze as well if it's showing up on the sides. Could simply be that the glaze is crazed and weeping through the cracks, or it could be that it's not matured. Link to comment Share on other sites More sharing options...
marshadohr Posted October 15, 2014 Author Report Share Posted October 15, 2014 I am now sure it was little loafers clay based on it's tannish color. I use several white clays and it matches the ones I am certain are LL. I glazed inside and outside. I poured the inside with Coyote Alabaster Satin ^6 glaze and sprayed the Outside with Casual Tones Merion Green ^6. The foot did not seem wet or sweating, though I could have missed it. The sandy surface over the glaze on the outside was quite distinct, tho. The outside did not look crazed though it did have little black specks and looked a bit pitted on some of the other pieces from that firing. My firing was slow to 2232 and 150 cool down to 1450. All seemed normal, but then this. Have you heard of anything like this before? Link to comment Share on other sites More sharing options...
bciskepottery Posted October 15, 2014 Report Share Posted October 15, 2014 Did it only happen with this glaze combination, in particular the Merion Green on the outside? If just this glaze, you might have a bad batch of glaze from Ceramic Supply (?) that is allowing something to leech through the vase walls. And, as it is a commercial glaze, there is no telling what the ingredients are in the glaze. Also, was your spray gun clean before filling with glaze? Could there have been a contaminant left over in the spray gun from prior use? Link to comment Share on other sites More sharing options...
neilestrick Posted October 15, 2014 Report Share Posted October 15, 2014 Pictures, please. Link to comment Share on other sites More sharing options...
marshadohr Posted October 15, 2014 Author Report Share Posted October 15, 2014 I am extremely careful about keeping my spray gun clean. As for the glaze, I have another vase I did the same except with a Rock River color and it pitted also. I have not filled it with water to see if it leeched through the walls. I can do that. This happened on a vase I bought from another potter and like(d) to use for flowers. I will fill a couple of other vases of mine with water and see if it might be the alabaster interior glaze. I want to end up with a cone 6 very white clay. I don't like the tan color of the Little Loafers which is why I switched to 1/2 and /12. I will fill my other glaze combinations with water and then photo them with the residue on the outside if it happens. I can try this vase again to see if I get the same dramatic goo. Thanks for all the help. Link to comment Share on other sites More sharing options...
Min Posted October 15, 2014 Report Share Posted October 15, 2014 Shouldn't make a difference if there is glaze on the pot or not. Vases etc should be able to hold water without weeping even when unglazed. Try firing a cylinder in each of the clays you use with no glaze inside or out then fill with water and place on a piece of newsprint for a few days. Paper should be smooth with no wrinkles. I would look at the body first then work on the glazes. Link to comment Share on other sites More sharing options...
marshadohr Posted October 16, 2014 Author Report Share Posted October 16, 2014 This is after 24 hours. It gets more pronounced with time. Link to comment Share on other sites More sharing options...
oldlady Posted October 16, 2014 Report Share Posted October 16, 2014 that is wierd!!! Link to comment Share on other sites More sharing options...
neilestrick Posted October 16, 2014 Report Share Posted October 16, 2014 Is the glaze crazed? If so, is the white showing up along the cracks? Link to comment Share on other sites More sharing options...
marshadohr Posted October 17, 2014 Author Report Share Posted October 17, 2014 No crazing. inside or out. Looks OK except for little black specks and almost pits. The other pieces in that firing small pits. Link to comment Share on other sites More sharing options...
bciskepottery Posted October 17, 2014 Report Share Posted October 17, 2014 Looks like the soda ash crystals that can form on the outside of a shino glaze. Little Loafers has nothing in it that would create the black specks. I'd lean towards contamination in the glaze, maybe a bad run from the company. Have you reached out to the glaze manufacturer and sent them the picture? They might be able to tell you if there is something in the glaze materials that could be causing or contributing to this. If they value you as a customer, they'll send you a new pint of glaze to see if the problem persists. Or they might ask you to send the bottle back and let them try it. Link to comment Share on other sites More sharing options...
neilestrick Posted October 17, 2014 Report Share Posted October 17, 2014 Is the bottom unglazed, and if so is it weeping out the foot? Put it on a piece of paper and let it sit overnight if you're not sure. If the water is getting through the glaze and the clay, then it should weep out the foot, too. It definitely looks like something soluble is coming out of the glaze, but at cone 6 the LIttle Loafer's clay should be tight enough that it wouldn't weep. Anything odd about your water? Well water, lots of minerals, etc? Is this happening to other pieces form the same firing with this same glaze? Do the crystals seem to start at the pits or black spots you mentioned? Link to comment Share on other sites More sharing options...
Min Posted October 17, 2014 Report Share Posted October 17, 2014 Kind of looks like a minor case of the fuzzies you get on plaster from soluble salts coming out. Link to comment Share on other sites More sharing options...
marshadohr Posted October 17, 2014 Author Report Share Posted October 17, 2014 Water is city water. Nothing odd there. Soluble salts might be there unknown to me. Yes, the foot is weeping. No, the fuzzies didn't happen on other pieces glazed in that load (with the same glaze) though there was pitting in all of them except this one --tiny "pimples" over much of the outside. The fuzzies don't seem to be originating anywhere in particular - more an all over thing. This piece had black specks but no pits. I'm thinking of re-firing the entire load, but wonder which temperature to do and what will happen to the glazes. Any suggestions? Also, here are the fuzzies at 48 hours. I will try the manufacturer to see what they say. Link to comment Share on other sites More sharing options...
marshadohr Posted October 17, 2014 Author Report Share Posted October 17, 2014 Now that I have declared that I used LL I have looked at a few other pieces that are weeping and I now think it was 1/2 and 1/2 for all the vases that weeped. The other vase that weeped badly was an earlier piece and the glaze was fine but the foot leaked like crazy. So, if that is the problem do I need to re-fire at cone 10 (which I have never done on this kiln). What will happen to the glazes I've used? Have I just ruined all my pieces? I have 5 lovely carved boxes that are green 1/2 and 1/2. If I fire them at ^10 is there an optimum bisque temperature? Does that affect the glaze (like the pitting)? I feel like I have learned nothing in the years I have been doing this. Or, rather, the more I learn about doing clay art the more there is to learn. Wish I were in my 20s!! Link to comment Share on other sites More sharing options...
Min Posted October 17, 2014 Report Share Posted October 17, 2014 If by chance the clay is Laguna's 1/2 & 1/2 I would check you have the ^5 version. It has 0.5 (+ or - 1%) absorption so they should be fine if fired to ^6. Do you have the box number? The western ^5 one is WC402 , the ^10 one is WC382. If it is the ^10 one then just bisque them the same as you would for ^6 clay (but use a ^10 glaze when firing to that). For the boxes, if they don't need to hold water and you used the ^10 clay you could just fire to ^6 since they don't need to be tight. Fingers crossed it's not the ^10 clay! Link to comment Share on other sites More sharing options...
Babs Posted October 17, 2014 Report Share Posted October 17, 2014 Looks like they are emerging from crazing. Could be in the clay body.(solubles) Link to comment Share on other sites More sharing options...
marshadohr Posted October 17, 2014 Author Report Share Posted October 17, 2014 The box says Highwater half and half. cone 6-10. No numbers. Link to comment Share on other sites More sharing options...
marshadohr Posted October 17, 2014 Author Report Share Posted October 17, 2014 Highwater: Half Phoenix - Half P10. Laguna: doesn't say which stoneware or which porcelain. Definitely has a ^5 and a ^10, tho. The studio where I have taken some classes has decided to only fire to Cone 6. They are telling students that Highwater Half and Half is fine at that temperature. I will continue with my boxes because they do not need to hold water, as you pointed out. The vases, tho.... What will happen to my ^6 glaze (which is obviously already on them) if I re-fire them at ^10? Link to comment Share on other sites More sharing options...
Min Posted October 17, 2014 Report Share Posted October 17, 2014 My bad, when I read 1/2 and 1/2 my brain jumped to Laguna's clay with the same name. In any event like Bruce said it will be porous at ^6 which would account for water seeping through it, pulling some soluble salts with it and growing those fuzzies. Not responsible for your instructor to say it's okay at cone 6 without qualifying it by saying it will be immature and weepy. There are some ^6 glazes that can go to ^10 but the majority of them can't. Blisters, overly glossy, thin and probably running off the pot are more likely scenarios. If you test the glazes you have then put the test tiles in a saucer of clay to catch runs. Dried flowers in the vases? Link to comment Share on other sites More sharing options...
bciskepottery Posted October 18, 2014 Report Share Posted October 18, 2014 Highwater's Half and Half has a 5% absorption rate at Cone 6 -- not even close to being mature. http://www.highwaterclays.com/index.cfm?fuseaction=product.display&product_ID=255&ParentCat=34 Your studio is going to have a lot of weeping/seeping pots. If they want to fire to Cone 6, they should use a Cone 6 clay. Refiring at Cone 10 will likely see your glazes run . . . they are not formulated for that high of a temperature. If you feel the need to try refiring one at Cone 10, make sure you have a large cookie with a rim underneath the item to catch any glaze. As Min suggested, dry flowers are an option. And find another clay body if your are firing at Cone 6; Highwater has a cone 6 porcelain; maybe mix it 50/50 with Little Loafers. FWIW, I use Highwater clays. I sometimes put a porcelain slip over Little Loafers if I need a white color. Link to comment Share on other sites More sharing options...
neilestrick Posted October 18, 2014 Report Share Posted October 18, 2014 Yep, they need to switch to a cone 6 body. Link to comment Share on other sites More sharing options...
Chilly Posted October 18, 2014 Report Share Posted October 18, 2014 Dried flowers in the vases? I made a terracotta vase/pencil pot for a birthday gift (in a hurry) with no time for a glaze firing. I took the finished vase to the supermarket and tried all the plastic bottles (coke/lemonade/milk ......) until I found one the right size and bought it. I then cut the bottle down so it was just lower than the rim of the vase and said to my friend that if she wanted live flowers she needed to use the liner. Link to comment Share on other sites More sharing options...
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