First bisque fire

[mkelly2]

Hello! Newbie here who just did her first bisque fire ever. I have a Cress FX23p kiln with a kiln sitter. The commercial glaze that I have purchased says to apply to 04 bisqueware and then fire to cone 5 or 6. So I set my kiln sitter up with a 04 junior cone, loaded up my greenware (after much arranging and rearranging of furniture) and witness cones, and fired her up! 

I've attached a photo of the witness cones from the top and middle shelves (my kiln only has 2 peep holes so I did not place any on the bottom shelf since I wouldn't be able to view them). I had a brain fart when lining the cones up, so from left to right its  top shelf 05, 04, 03, and then bottom shelf 05, 04, 03. I realized after the fact that I should have lined them up 03, 04, 05. Worried that the 04 witness cone did not bend far enough, I did some research and found that perhaps I should have used a 03 junior cone as the junior cone will bend quicker than the witness due to the gravity of the actuating rod. The pieces came out looking like bisqueware of course but I am worried about applying the commercial glaze since it calls for it to be applied to 04 bisqueware. Should I go ahead and apply the glaze anyway?

Thank you in advance!! Let me know if you need more info provided.

[Hulk]

Hi M!

Close enough would be my opinion, however, if the clay(s) in question are red, brown, black, enough time and oxygen to burn out the organics may be at issue - even buff or light brown clay may come out better with extra time and air. Also, if your pieces are thick/heavy, more time and air can help.

Back to close enough, your 04 has a bit o' bend, that is close!

For your glaze run, +1 in the sitter matches my (limited) experience. Early on, I watched cones through the peeps, watched the pyrometer read out (worthwhile investment, that), and kept notes. I didn't trust the sitter, and still don't, however, I still set it up each time and dial the timer as well, just in case somewhat happens and I'm not right there "on it" during the last hour of firing. Watch the cones would be my advice.

Be sure to wear good and proper (against the harmful rays and any flying bits) kiln glasses.

[Callie Beller Diesel]

So I have another Cress Firemate model, and I have found with mine that the cone sitter tends to fire true, especially if the rod isn’t corroded and hasn’t lost any diameter. It looks like yours shut your kiln off perhaps half a cone early, which is actually pretty close. It could be fixed with a short soak hold of maybe 10 minutes after the kiln shuts off. As Tom mentioned, definitely go by your visual cones until you can figure out what’s going on. I am less pleased with my pyrometer than he is with his though. I  find mine reads quite hot and shuts off well before I can get a read on the top end of my glaze fire.  I didn’t spend a lot on mine, though: I just got a $90 one from Amazon, so maybe there’s a brand difference at work there. 

If you’re finding you need to use a hotter cone in the sitter, what might work better is recalibrating the sitter. Sue McLeod has a really great tutorial on how to do that here: https://suemcleodceramics.com/how-to-calibrate-your-kiln-sitter-for-accurate-firings/ . All you need is a very sharp pencil and a screwdriver.

 

[mkelly2]

Hi Callie,

I have come back to your comment as I get ready to do another bisque firing (Its been a while since my last one so I am refreshing myself on what to do) and I have to ask, how does one do a soak hold on a manual kiln? I am in a few facebook pottery groups and people are always talking about doing holds - which I assume is a straightforward process if you have the fancy kilns that you can create programs for - and it leaves me scratching my head. I've tried googling how to do this with a manual kiln but never find a direct answer.

[Hulk]

Hi again M!
I watch the pyrometer (per prior, above) and twiddle the switches - my kiln has three knobs, top, middle and bottom sections, and each can be set high, medium, low.
Now that I've a few years of firing notes to refer to, it's easier, but no getting around checking frequently and setting the knobs at the critical junctures.

For warming off moisture afore bisque firing, I run up to almost 200F the night before, leave a few bungs out, and then full gas next day, closing up after a short while. It's working for me, but my wares are not thick, big, or massy.

For holding at 1500F, I'll set to low, then reset high, low, etc. every few minutes until the time is up, watching the pyrometer.

Reaching peak temps and drop and hold (for glaze fire), similar approach, just have to be there.
Hanging around the kiln isn't good if there's any deficiency in the ventilation plan - kiln fumes are not good.
A pyrometer, cones, kiln glasses, notebook, time and experience, and outstanding ventilation, go!

[Callie Beller Diesel]

To do a soak hold at the end of a firing in a manual kiln, you have to lift the hammer on the cone sitter, push the button in again to turn the kiln back on, and VERY gently lower the hammer again. You will now have to manually turn your kiln off at the end of your desired soak time, because you have just circumvented a safety shutoff. Be sure to set a timer for yourself!

I do a drop and hold cycle on my glaze fire, but I judge my kiln temperature by colour as to when to turn it back on. But there’s not a lot of us who do this. Usually for me, it’s about an hour after it finishes, but kiln pack and size will make your mileage vary. For anyone who is newer to firing kilns, this is where a good pyrometer would be a much better approach.