[How do I know if bisque is underfired?]

Min—thank you! I appreciate all of this thoughtful advice. 

I will let you know what happens.

-Lauren

[How do I know if bisque is underfired?]

1 hour ago, Bill Kielb said:

Just a couple thoughts
1200 f is about cone 020 ( likely not very sintered), folks who intentionally carve soft bisque end up around cone 012. 1860f is cone 05 / 06 so you likely would notice a big difference between the products including: look, touch, size, firmness, absorption, tongue test …… from 1220 f - 1860 f lots of things burnout including sulphur, calcium carbonate, etc…  but they don’t burnout necessarily because of peak temperature. It’s rather time at elevated temperatures so bisque firings are generally slower than glaze.

• You could bisque something to 1200 and compare
• You could re-bisque the pieces in question to let’s say cone 06 to be sure
• You could slow your glaze firing schedule through 1200 - 1860 as sort of a modified once fire schedule. Slow bisque schedules generally go about 180 f from 1000f to 1700 f btw.

I do not believe your actual glaze temperature has been referenced yet. What cone do you glaze fire to? Some of the above more or less assumes you glaze to cone 5/6.

Cone 020 is really a China paint type schedule generally designed to just begin softening glaze, I think the bisque would be incredibly soft at this temperature and not very sintered, but easy to test to be sure.

Thanks Bill! I am unfamiliar with (but now learning about) soft bisques.  Yes, I glaze to 2175F, and after a 12 min hold it's around cone 6.

I like your idea of the 1200 tests, but because this work is time-sensitive (and I have a lot of other firings going on), I'm more inclined to just redo the pieces.

As for the rebisque, I am reluctant because it risks cracking the piece, but perhaps it's worth a shot. 

Your third suggestion is appealing. My bisque schedule goes 100f/hr from 1200–1860 so maybe I just insert that into the glaze.

 

Thanks!!

[How do I know if bisque is underfired?]

4 hours ago, Min said:

@Lauren F, what cone are you firing the tiles to, cone 6? How are you firing the tiles? How big is the kiln, room to put a shelf above and below the one(s) that will have the tiles? Can you slow cool the kiln?

 

I fire these to cone 6, in a pretty fast firing. The kiln is on the larger side (https://coneartkilnsshop.com/index.php/product/2827d/) 

Yes, I could slow cool it.

[How do I know if bisque is underfired?]

Thanks so much Min and Kelly—this is incredibly helpful! I am really grateful.

Unfortunately I have already glazed all of the bisqueware I have in this particular clay body (white stoneware mixed with molochite) so I don't have an ideal point of comparison. 

I did the tongue test on some correctly-fired bisqueware of another body and I did not notice a difference. Did the same with water and noticed a slight difference.  Also, the bisqueware in question doesn't yield to a wooden tool, so that is a good sign! Yet it does seem pinker than some of the other bisqueware I have lying around, but because it's a different clay body, I can't be sure that's abnormal.

In addition to making a couple backup pieces, my plan is to glaze the work as planned but modify the schedule to move slowly on the ascent around 900-1200F.  Any thoughts on this strategy would be appreciated. 

 

[How do I know if bisque is underfired?]

I recently fired several large greenware tiles (20 x 20") in a custom pre-programmed slow bisque. They came out fine.

When I loaded another bisque today I noticed that this same pre-programmed slow bisque schedule was missing the last segment (to 1860F). I am not sure when or why this was deleted, but I am worried that the previous tiles may not have reached full temperature. In this abbreviated schedule, the final segment was set to 1200F.

My question is—would I be able to tell if the tiles were fired to 1200F instead of 1860F? 

[Light rutile]

Hi—

I just replaced my light rutile supply with something called "ceramic rutile" which I was told is the same. 

Back in the studio, the new batch looks significantly darker. Before I run tests, does anyone have any experience with light rutile or ceramic rutile? Are they the same and does the subtle color difference matter?

Thanks! 

[Price of Lithium]

Seems like the global price of lithium is (thankfully!) dropping as of last week.

Anyone know how long it will realistically take for this to affect ceramic suppliers? I'd like to invest in a large quantity at some point soon....

[Spray Booth Setup: Ventilation Fan]

I flipped the fan over today and it works perfectly. Wonder why the manual indicates otherwise…?

I would still be curious if anyone else has encountered this issue. The next idea I had was to reverse the direction of the fan, which seems possible. Has anyone tried this?

[Spray Booth Setup: Ventilation Fan]

I recently set up and installed a new Laguna Pro-V spray booth with a (also new) 1720 CFM Dayton 4C659 tubeaxial fan (included from Laguna). The fan is ventilated outdoors via simple ductwork. However, when I turn the fan on, it is barely sucking air. Generally, these machines are quite powerful, so something seems off. Although I believe it's installed correctly, I suspect that it may be upside down, despite clear instructions on the fan and in the manual on how to orient it. 

Does anyone with this spray booth have any guidance on which way to orient the fan or if there is possibly something else wrong? I am hopeful that the fan is not defective and there is some quick fix that I just overlooked.

Attached is a current and installation photo of the fan as well as a diagram from the manual.

-Lauren