I do a lot of layering, sometimes good, sometimes not so good.  I usually do tests on a tile first & then pick a few combos & put them on a throw away pot.  After that I will use it on a good pot.  Lately, I have been having some crater/pinhole problems.  It started with certain combos using some Spectrum glazes.  I have been respraying & refiring the problem areas, but then other areas pop up.  A couple of these pots have been glaze fired 5 times.  Does anybody out there have a magic glaze that will make these other glazes behave, since I can't take them off the pot?  Is there a glaze that I can pack into the craters that will make them smooth out?  Is it a clay problem?  I always do a 15-20 min. hold at the end of the cycle.  I have even had a few pinholes on a controlled cool down as well.  I wonder if it is time to get the hammer out.  Any help would be greatly appreciated.  Thanks,  jhp

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Jeff, you might increase your soak time to 30-45 minutes, and do a controlled cool down. Also, be vigilant in having a smooth clay body after you trim, take a soft rib and burnish the clay body, as pinhole and craters get their start in pits on the clay body. Finally, you can play with your bisque temps. I have heard recommendations to bisque to 04 to help with pitting, however, I bisque to 06 and have few if any problems. Re-firing usually is not the best answer. By the way, nice pot in your profile picture!
Hey Michele,
Thanks for the reply. I will try a longer soak. I do all my bisque to ^04. I tried doing fast bisque, but had more problems so I went to a medium bisque. Maybe I should try a slow bisque & try to burn more organics out. What about packing the craters with an earthenware glaze & firing to a hot ^04? I seem to have more problems with the Laguna Santa Fe which is a coarser clay, so maybe I should try a soft rib like you say. I just tried a new clay the other night, Apaloosa from Coyote. It throws like no other, so we will see how it bisques & takes glazes. I think your blues & turquoises have got it goin' on! I usually don't do 3 footers, but this lady insisted on a 3' vase. I just wish she had let me pick the colors, but she just wanted brown colors. I do more for the blues, reds & purples. Later, jhp
Arrrrg! I'm having the same problem and don't know how to "fix" it. Glazes that I have been using successfully are now pitting. The only thing I have changed is my thermocouple. I have witness cones in my firings and they are getting to temp. I'm thinking the only other thing to do is to put new elements in my kiln. I'm slowly going crazy as I've ruined 2 loads of ware.

I've re-sieved my glazes, vacuumed the kiln, made sure my glazed pieces have dried before firing, I bisque to ^05 (normal for me) fired to ^5 with 15 minute soak (normal for me) even fired to ^6 and nothing seems to work. This is not the time of year to work out failure of kiln firings!

Any suggestions?

Ceci
Hi Ceci,
I had to change out my elements & TC last Saturday. It could not even make it to ^8. The last firing to ^5(before changing the elements & TC) on the same 3 pots yielded worse results. I had taken a popsicle stick & packed the craters & pinholes with a dried out glaze that I had(Spectrum Reactive Light Blue). While the pots get better looking with each firing, it is not getting rid of the craters. When I pulled the TC out Saturday, it was kind of stuck. I am guessing that the people that I bought this kiln from must have bent the TC at some point as the little ceramic spacers were cracked & the TC was still bent & one leg had corroded to almost nothing. I don't even know how it was even working. Ever since I have had this kiln, it has always fired hot. Now that I have new elements in & TC, I will have to see how it behaves. I have only done one crystalline firing since replacing the elements, so I really don't know what it is heating to according to cones. I do know that it makes it to top temp a lot faster & I had plenty of crystals, too many in fact. What I want to try next is to take the 3 pots & pack the craters again with an earthenware glaze & fire it to a hot ^04 with a 45-60 minute soak & see what that does. I have some Milky Clear that is somewhat dried out & it would be easy to pack in the holes & it can fire anywhere from ^04 to ^6. In the past when I have had a problem with craters, I have reheated the piece to about 150-175 degrees & sprayed it with Mardi Gras or Smokey Blue & then refired to ^5 with a 20 min. soak & everything has usually laid right down. That ain't workin' lately. I will try the low-fire approach & keep you posted. I know that the TC was part of the problem & maybe things were getting too hot, especially glazes with rutile/titanium in them, so with a bad TC, a longer soak made it worse. In fact, now that I think about it, the best refire to get rid of craters was one night when I was too tired to stay up & let the kiln finish, so I shut it off early & went to bed. In the morning when I pulled it out, no craters!
Almost forgot, I am way envious of your layering skills! jhp
Hi Jeff

I'm thinking maybe I need to replace the relays. Don't know what else to do. Let me know how your firing goes. Thanks

Ceci
I have wondered too about my relays as I sometimes think I hear them cycling a bit too much. I was going to replace them with an SSR & change over to an "S" TC this time around, but I would have had to send the board back to have it modified & I didn't have another kiln up & running & I couldn't be down for that long right now. It will have to wait until spring now or when I have some down time. Relays sticking open, not so bad. Relays sticking closed when you're not around, meltdown! SSR's are also a lot easier on your elements. Oversimplified, it's like having a dimmer knob on a light instead of just an on & off switch. jhp
OK, now I got a new problem. I thought I would try some of the new Spectrum Electric Ash glazes. Everywhere they went, they produced lots of little bubbles & ruined what were some decent pots. Any ideas? I fired a fast ^5 with a 30 min. soak which gave ^6 just starting to bend. It says these are for ^4-6. Should I have gone hotter? The glazes under them were all Amaco PC glazes. jhp
I think the bubbles kind of go with the ash glaze territory. With the Hannah's fake ash glazes they tend to occur where the glaze gets thick. I don't know of a full cure, but have not felt the problem to be too severe to stop using the glazes. If you lightly spray another glaze layer over the ash glaze it may help, but will also reduce the characteristic rivulets that are the reason for using ash (&fake ash) glazes.
Hi Jeff

I refired my bisqued to ^04 to burn out more impurities. I haven't done a glaze fire since the last disaster but my kiln guy is coming tomorrow afternoon to replace my relays. I am going to re sieve another glaze that I've had problems with. I will do a glaze test fire tomorrow after the relays are replaced.

I'm wondering if your fast fire with the 30 minute hold is too fast/hot. When I use Amaco PC glazes I fire to ^5 with a 15 minute soak and usually it's fine....(not now though...take into account my current kiln issues). My kiln guy mentioned that since the only thing that has changed was my new thermocouple...my kiln could now be firing more effectively and hotter. However the witness cones have all been on the money. He will check things out and maybe I'll have answers tomorrow. I can only hope. Will let you know how it goes.





Jeff Poulter said:
OK, now I got a new problem. I thought I would try some of the new Spectrum Electric Ash glazes. Everywhere they went, they produced lots of little bubbles & ruined what were some decent pots. Any ideas? I fired a fast ^5 with a 30 min. soak which gave ^6 just starting to bend. It says these are for ^4-6. Should I have gone hotter? The glazes under them were all Amaco PC glazes. jhp
Hi Ceci,
I have fast fired the PC glazes before & never had a problem. I usually soak for about 20 minutes. What I am wondering is if there is something in the Spectrum glazes that either has a heat issue or a chemical issue. I didn't have the extreme crater issues until I tried a couple different layers with Spectrum glazes & now when I put their ash glazes on glazes that haven't had problem before. and presto, I have problems. Like George said, a few bubbles go with the territory, but this is more like marshmallows melting in hot chocolate. The common denominator so far is the Spectrum glazes. Maybe its the heat or speed, or maybe there are some chemicals that don't play nice together. Like George says, I will try a light spray over the top & see what happens. It will probably dilute the rivulet effect, but if it gets rid of the bubbles, I'm all for it. I wish I had a kiln guy, then I could of had him finish the roof over the kiln yesterday instead of me out there freezing. The only good thing is that the kiln was on its way down, so I only got cold when I was cutting supports & panels & I could warm up when I was installing them. None too soon either as they say the snow level will be dropping tonight & tomorrow. The temporary roof was OK for rain, but it would not have held up with the snow. I will hopefully get some earthenware glaze slathered into the craters this week & get those 3 acne leftovers refired. I think I will spray some Mardi Gras over the ash & see what that does. Mardi Gras has a good history of helping glazes lay down nice. Will keep you posted. Let us know what the kiln guy says. BTW, the last 2 bisques I have done, I did on slow. It is agonizing to wait that long. The most I can get I can get in my little 818 is 3 pots, sometimes only 2 & sometimes only 1. I have got to get the other kilns up & working, but it will have to wait until spring. jhp
P.S. What clay are you using?
So I fired a couple more pots last night. PC glazes layered with Spectrum Electric Ash over. Fired to ^6 with a 15 minute hold. The Ash had less bubbles in it, but to my eye the PC's looked a little on the done side. I didn't have cones in, `cause in my haste to get the building materials back in the shed out of the rain & snow, I inadvertently buried my box of cones. I will have to dig them out tonight, now that is has cleared off for 5 minutes, & do another firing with cones in. The crystalline firing that was in Saturday night/Sunday day came out just fine. I don't think it is a temp issue, I think it is a chemical issue. I have some Amaco Ash glazes coming & will see if they behave the same way. jhp
Hola Jeff

Hmmmm yeah, I fire to ^5 with 15 min soak. Since your crystalline glaze fire came out good maybe it's time to dump the Ash glaze and mix your own of find another brand. Sucks I know. I just got rid of 3 gallons mixed coyote gun metal green glaze that did not fit my clay body. My supplier said they didn't change the recipe of the clay but I'm not willing to ruin (and I mean really ruin) more wares. I'm using Georgies G-mix which is the equivalent of Lagunas B-mix.

Kiln guy will be here in about 45 minutes so I'm looking forward to hopefully having some answers. Will probably do a test glaze fire tomorrow and let you know the results.

Ceci



Jeff Poulter said:
So I fired a couple more pots last night. PC glazes layered with Spectrum Electric Ash over. Fired to ^6 with a 15 minute hold. The Ash had less bubbles in it, but to my eye the PC's looked a little on the done side. I didn't have cones in, `cause in my haste to get the building materials back in the shed out of the rain & snow, I inadvertently buried my box of cones. I will have to dig them out tonight, now that is has cleared off for 5 minutes, & do another firing with cones in. The crystalline firing that was in Saturday night/Sunday day came out just fine. I don't think it is a temp issue, I think it is a chemical issue. I have some Amaco Ash glazes coming & will see if they behave the same way. jhp

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