Kellykopp Posted February 9, 2022 Report Share Posted February 9, 2022 I fire a slow cool program and still have pinhole issues...not a lot, but enough to drive me nuts. Top temp is 2150 with a 15 minute hold. My kiln fires @ 25 degrees lower then what the readout tells me. My conepacks tell me the kiln is firing consistently a hard ^5/soft ^6 (except for the very top of the kiln, which is ^5, and I place ware there accordingly). I wipe my ware off before glazing. My question is: would it benefit more to alter my peak temperature by 5 or 10 degrees, or lengthen the hold time by 5-10 minutes to try to get rid of the pesky pinholes? I am getting ready to fire a "dummy" load, with a few sacrificial pieces in it. Any suggestions would be very welcomed. Thanks! Link to comment Share on other sites More sharing options...
Babs Posted February 9, 2022 Report Share Posted February 9, 2022 Pictures would help. What clay do you use? What cone do you bisque to? How thick are your glazes? Could slow down the last 100degC of firing to help glaze mature. Link to comment Share on other sites More sharing options...
dhPotter Posted February 9, 2022 Report Share Posted February 9, 2022 What Babs said. When going up to top temp at around 2050*F slow the ramp down to 108*F per hour. Do your hold at top temp. Let the kiln free fall to 2050*F then hold for 20-30 minutes. Then continue with your firing schedule. Should clear up pinholes. Link to comment Share on other sites More sharing options...
Hulk Posted February 9, 2022 Report Share Posted February 9, 2022 drop and hold is working well for meDrop-and-Soak Firing (digitalfire.com) Link to comment Share on other sites More sharing options...
Russ Posted February 9, 2022 Report Share Posted February 9, 2022 The drop and hold allows the pinholes to heal over while the glaze is still in its fluid state. Link to comment Share on other sites More sharing options...
Kellykopp Posted February 9, 2022 Author Report Share Posted February 9, 2022 Sorry for the long delay in getting back to your questions. Had to take my mom to wound care, did not mean to be rude. I don't have a camera, or "smart phone" so I am sorry I can't send pics, sorry about that. But rest assured they are pinholes. I have used several clays in the past, the current clay is Kentucky Mudwork's Iceman. In the past, Little Loafers. All ^6. All commercial glazes, Coyote, Amaco, Kentucky Mudworks, Mayco. I bisque to ^06. This is the firing program: (Fahrenheit) 100 to 220 350 to 2000 120 to 2150 hold 15 minutes 500 to 2000 hold 5 minutes 300 to 1750 125 to 1400 Glazing normal coats, usually brushing 3. Thickness of the glaze doesn't seem to matter...had an Amaco celedon pinhole a little at 3 coats. Generally follow manufacturer's recommendations. I was thinking of a longer hold but just wasn't sure where to apply it for the glaze to have "heal" time. Link to comment Share on other sites More sharing options...
Kellykopp Posted February 9, 2022 Author Report Share Posted February 9, 2022 P.S. You people are the best. Thanks for the kindness of your replies. Link to comment Share on other sites More sharing options...
Babs Posted February 10, 2022 Report Share Posted February 10, 2022 Change one thing at a time. 1. If not bisquing to cone 04 do that. Do your usual glaze program Sorted...fine. Not sorted Try next strategy... Slow last ramp to cone you want. Then DH potter & Hulk's strategy. Are the pinholes shartp edged? Some glazes need to be fettled a bit to smooth out thick bits which may pinhole Link to comment Share on other sites More sharing options...
Kellykopp Posted February 10, 2022 Author Report Share Posted February 10, 2022 Yes Babs, some (but not all) pinholes have rough edges, which leads me to believe that they haven't had time to heal. Any lumps in the glaze are removed as I see them. The coats are applied as evenly as possible. I was already considering bisquing to ^05 as I have read that may help, thank you for re-affirming that point. I am loading the dummy kiln today and think I will tweak the program to hold for 15 minutes at 2000, then another 5 minute hold at 1750. I realize this will increase the heat work in the kiln. Does anybody know if there is a chart or formula that can be used to figure out time/temp/heatwork? I don't want to overfire the work by holding it too long. Sorry to bother you all and I appreciate your help. Link to comment Share on other sites More sharing options...
Babs Posted February 10, 2022 Report Share Posted February 10, 2022 It is poss if pinholes are rough that they are blisters..i.e. overfired! Without seeing them it makes it hard. If you get to temp then hold for 15, you can go up a cone quite easily . Some glazes won't like that if close to overfiring.... You can't get a friend to photo the pots? Are the holes occurring everywhere i n kiln in every glaze? Anyway, change one thing at a time is way tI go and take notes of your firings. Link to comment Share on other sites More sharing options...
Kellykopp Posted February 10, 2022 Author Report Share Posted February 10, 2022 Don't really think overfired, my cones tell me consistently I am at a hard^5/soft ^6 ( ^5 down, ^6 half down). Pinholes consistent., all glazes, all areas of kiln. I always take notes, and the kiln always fires evenly as I check/record the thermocouples (kiln has 3 zones) several times each firing. I am running this dummy firing holding 10 minutes at 2150, holding 10 minutes at 2000, and holding 5 minutes at 1750. Conepacks on each shelf to tell me actual heatwork. Keep your fingers crossed for me! Link to comment Share on other sites More sharing options...
Hulk Posted February 10, 2022 Report Share Posted February 10, 2022 Perhaps related to higher bisque target (hotter), adequate oxygen. I'm running a powered kiln vent/fan, which pulls a small stream of kiln atmosphere out the bottom, hence, ambient is pulled into the kiln. Oxygen, purportedly, is important for thorough bisque. Some advise leaving the top bung out, for ventilation, if a powered vent is not in use. Perhaps related to higher bisque target, holds; for red, black, and buff clays, I've added significant hold at 1500F - more time to burn off all the yuck. It really helps; I'm holding for thirty minutes or so. Cones (on each shelf) should tell the story on heat work achieved (ah, you're doing that!). My advice there would be to set cones (at least target cones) on each level for glaze fires, and if not each level for bisque fires, then one or two levels. I've used several clays that fizz/bubble/outgas much more at cone six vs cone five. Perhaps more heat work is necessary; however, my guess would be no on more heat work. Dropping 100F from peak, then holding for thirty minutes doesn't seem to move the cones at all. Link to comment Share on other sites More sharing options...
Bill Kielb Posted February 10, 2022 Report Share Posted February 10, 2022 6 minutes ago, Kellykopp said: Pinholes consistent., all glazes, all areas of kiln Pinholes in all glazes all areas would indicate even glazes that heal well are pinholing and it make me want to try an 04 bisque in the 12 -15 hour range just to be sure there are not significant organics bubbling about. I know you bisque to 06, but how long is also important in order to burn out all organics. Link to comment Share on other sites More sharing options...
Kellykopp Posted February 10, 2022 Author Report Share Posted February 10, 2022 Thanks Hulk, my kilns are vented, and I use them each firing, bisque and glaze. Always have used conepacks on each shelf as well (even though kiln is digital, I have always used them to ascertain the actual heatwork) I am "spreading out" the holds on this dummy firing, am taking the 2150/15 minute hold and reducing the hold to 10 minutes. Am taking that 5 minutes and moving it to the 2000/5 minute hold and making it a 10 minute hold. Then adding a 5 minute hold at the 1750. Link to comment Share on other sites More sharing options...
Kellykopp Posted February 10, 2022 Author Report Share Posted February 10, 2022 Thanks Bill, certainly something to seriously consider. The ^06 bisque is the "slow" bisque program already in the kiln. It takes generally 12 and a half hours to fire. When I get more ware ready, I am going to try a higher bisque. Problem is, I have 4 more kiln loads already bisqued at ^06, and I would hate to lose that much production, hence trying out the drop hold to see if that works any. The problem isn't serious, but enough to aggravate me, as I tend to want things as perfect as possible. Link to comment Share on other sites More sharing options...
Bill Kielb Posted February 10, 2022 Report Share Posted February 10, 2022 6 hours ago, Kellykopp said: I have 4 more kiln loads already bisqued at ^06, Not a total loss, you can rebisque them, so maybe take a few from there and some newly made to 04 then glaze. Link to comment Share on other sites More sharing options...
Babs Posted February 10, 2022 Report Share Posted February 10, 2022 Cones self supporting or not? Some one recently pointed out that s.supp. are read differently to be read properly..... Test tiles with 1 coat 2coats and 3 coats can be done on same tile, can do a number in same load.... Then you can rebisque your bisqueware if necessary. Link to comment Share on other sites More sharing options...
Russ Posted February 10, 2022 Report Share Posted February 10, 2022 A 150 degree drop is a lot of cones. Do you think your glaze is still fluid at 2000f? Thats cone 03...ish. Your glazes may already be "frozen" by the time it hits 2000. Link to comment Share on other sites More sharing options...
Kellykopp Posted February 10, 2022 Author Report Share Posted February 10, 2022 Babs: conepacks not self supporting, I make my own as I was taught in the 80's (oooopssss, told on my age lol) but you are right, there is a difference in the self supporting vs the packs. Test tiles are a great idea as I have boxes of "blanks" running around the studio (when I make them, I make plenty to spare). Bill: insert me smacking my head with my hand here....now why didn't I think of that?....wonderful I really appreciate your input. That's what makes this forum so awesome. Different perspectives and ideas all being shared. I will tell you again YOU PEOPLE TOTALLY ROCK!!!!!!!! I deeply appreciate the help. Dummy kiln should be about done. After she cools off, tomorrow I will tell you all results. Regardless of the outcome, you all have given me numerous venues to check out to help me remedy the issue of these pesky pinholes. Link to comment Share on other sites More sharing options...
Kellykopp Posted February 10, 2022 Author Report Share Posted February 10, 2022 Russ, the firing schedule is loosely based on Coyote's slow cool program. I followed it one time with horrid results....very much over-fired. I have several avenues to explore now due to the insightful and helpful people who have taken their valuable time to point me in directions I need to seriously consider to achieve my goal. You are correct that the fluidity of the glaze has to be considered also. I am starting to feel that the issue may be a combination of factors that must be looked at, weeded out, and corrected. Link to comment Share on other sites More sharing options...
Russ Posted February 11, 2022 Report Share Posted February 11, 2022 If youre using Coyote glazes you might try giving Martin Butts a call in Albuquerque and ask him whats going on. If anybody would know it would be him. Im pretty sure you can find the number online for Coyote Clay there in Alb. NM Link to comment Share on other sites More sharing options...
Kellykopp Posted February 11, 2022 Author Report Share Posted February 11, 2022 Conepacks told me the kiln fired slightly less heatwork. Some teeny tiny pinholes still present. Gonna back up and punt. Hulk, what do you think of going back to the 2150/15 minute hold to get my heatwork back, then dropping to 2000 (which is really around 1975 due to kiln offset) and holding for 20 minutes? This will be for the next dummy firing. Babs and Bill: am gonna put some ware in my small kiln and bisque to ^04, glaze them, and put them in a dummy kiln to see what happens. Ware is already wax resisted, but should burn off no problem. Russ had a valid point also. Maybe I should do some ciphering and re-visit my top temp to make sure that I am not holding the program for no end results due to fluidity of glaze. I foresee lots of dummy firings in my future lol Link to comment Share on other sites More sharing options...
Babs Posted February 12, 2022 Report Share Posted February 12, 2022 If you had less pinholes with less heatwork, try for even less heatwork..your glazes may not like the amount of heatwork you are giving them and in fact be blistering if edges are sharp....worth a try. Link to comment Share on other sites More sharing options...
Bill Kielb Posted February 13, 2022 Report Share Posted February 13, 2022 On 2/11/2022 at 9:50 AM, Kellykopp said: Russ had a valid point also. Maybe I should do some ciphering and re-visit my top temp to make sure that I am not holding the program for no end results due to fluidity of glaze. just thinking This is a very valid point and the common thought is - for some glazes the fired surface tension and fluidity of the glazes prevents them from healing. Raising the peak temperature and / or holds at peak often make this problem worse. The drop and hold is sort of a trial way to lower the temperature and reduce the fluidity enough for these areas to flow together and heal. So how much to drop and how long to hold is the trial part. So when pinholes get worse with higher peak temperatures or counterintuitively get worse with longer healing holds at peak I think these are good candidates for the drop and hold. If reducing from cone 6 to 5 improves pinholes, then this is a good indication a drop and hold can be effective while still allowing one to fire to maturity for the cone 6 materials. Link to comment Share on other sites More sharing options...
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