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Member Since 31 Mar 2010
Offline Last Active Yesterday, 03:17 PM

#63115 Refring?

Posted by Min on 23 July 2014 - 05:28 PM

Another question. If you refire to your glazes maturation point could this repair pinholes without affecting the look of the piece to much? I suppose it would depend on how runny a glaze is?


I hate pinholes, they turn up in all the wrong places don't they? Yup, refiring can smooth over pinholes but not always. You can rub a tiny bit of dry glaze into the pins and refire. I would put those pots in the coolest area of your kiln if possible. Yes, most glazes do move more on subsequent firings to similar cones. Sometimes they look better, sometimes not so much.


Couple other thoughts about pinholes if they are a real problem, apologies if you already know this stuff.


- clean bisque firing to around 05 - 04 with good ventilation, avoid stacking pots inside each other


- sub out any ingredients that have a high loi rate, for example if your glaze has a large amount of whiting it helps to reformulate glaze to use wollastonite in place of it (and some of the silica). Talc and dolomite have high loi rates also. Can't always get rid of them but helps if you can swap for something else like frit 3249 to supply the magnesium for example.


- glazes with high viscosity take longer to heal over the pins. Longer soak at the top temp without over firing sometimes helps.

#62895 To Share Or Not To Share

Posted by Min on 20 July 2014 - 07:45 PM

I think my presence here is testament as to how I feel about sharing. You will notice that I refrain fromtalking much about glaze and clay chemistry. I don't know enough, so I leave it to those that do (sensei John). I loved teaching, and here I can still help someone.


Maybe this is the thread summed up in a nutshell. We share what we are comfortable to share. 

#62516 Trimming Lids.

Posted by Min on 15 July 2014 - 07:07 PM

I don't use a chuck, throw upside down then trim right side up on a neoprene disc. Piece of firm foam in center to stop from deforming it if I'm throwing a knob on. Flange on the lid, no gallery on the pots.

#62277 Getting The Perfect Gloss From Terra Sig.

Posted by Min on 12 July 2014 - 11:39 AM

Was re-reading Vince Pitelka's terra sig article this morning. Near the end of the article he speaks about the glassy surface achieved by the ancient Greeks with no burnishing. 


This is the first paragraph, he goes on for several more expanding on this theory.


"Is it Possible to Make a Terra Sig that will Develop a Gloss with No Polishing?
I believe that my reference to "super refined terra sig" is appropriate in the context of other contemporary studio terra sig processes, but it recently came to my attention that the glassy surfaces on classic ancient Greek red-figure and black-figure wares were achieved with little or no polishing, and thus the terra sig must have been refined to a far greater degree. Recently I was contacted by a man conducting experiments to create such a sig. His process started out like mine, but after concentrating the liquid back to a specific gravity of 1.20, he repeated the whole process again, and again, and again, I believe about ten times. This process is ripe for experimentation. On the second and subsequent siphonings, you wouldn't encounter any distinct layer of identifiable sediments, and would have to simply sacrifice some arbitrary amount at the bottom of the settled mixture each time - again, an area for experimentation. The beauty of this process is that on the way to re-concentrating the suspension to a specific gravity of 1.20 after each siphoning, you could pause at 1.15 and try out a bit of sig on a piece to check the degree of spontaneous gloss.


Rest of the article is here: http://iweb.tntech.e...l/terra_sig.htm

(bottom of the article is the Greek subject)



#61966 Ways To Sign Your Pieces?

Posted by Min on 07 July 2014 - 09:20 PM

I had a stamp made at Jet stamps, they use acetal, a hard plastic, which makes a very crisp, burr free impression in the clay. They have a fast turnaround time and can help with design if necessary.


#61735 Cones Or Rods For Kiln Sitter? Which Ones?

Posted by Min on 03 July 2014 - 05:35 PM

 The clay I bought can be fired anywhere from cone 6-10, and all of my glazes I'm considering are either 6 or "5-6"


Are you making functional pots with this clay? A ^6 clay can't go to ^10 without bloating or warping and a ^10 clay will be underfired and porous at ^6. No worries if it's for sculpture but not advisable for functional pots.  A clay rated at ^6-10 might be okay at the higher temps but not at the lower. I would look into a clay rated as ^5 or ^6 if you are using glazes in that range.


As dhPotter said, since you are considering ^5-6 glazes then I would get 5, 6, and 7. For bisque I go to ^04 (for a ^6 or ^10 clay) For a sitter use bars, for witness cones use the full size regular or freestanding ones. (regular ones are cheaper and it only takes a few minutes to make the clay bases to place them in, just get the angle right). For the glaze firing I would use a ^6 bar but watch the witness cones.

#61489 ? Secret Ingredient In Underglaze?

Posted by Min on 28 June 2014 - 09:10 PM

I've tried a few underglaze bases, none of them have worked as well as Spectrum underglazes. Spectrum sells their underglaze base to which you add stain in approx a 2:1 ratio. (500 series base)


#61362 Tips & Tricks

Posted by Min on 25 June 2014 - 11:38 AM

It's been a while since we have had a tips and tricks posting and it's seems to be a bit quiet on the forums so anybody have anything new to share?


I've got this one: for pots that have gotten to dry to cut the rims of or attach handles to, wet cheesecloth works really well. I dip the cheesecloth in water then squeeze out the excess and drape 2 or 3 pieces on the area of the pot that needs to be softer. For fairly thin pieces it takes about 15 minutes and the clay is soft enough to work again. For thicker pieces I re-wet the cheesecloth and reapply. This works much better for me than misting or dipping the pot in water.

#61137 Plaster/hydro-Stone Bats

Posted by Min on 18 June 2014 - 09:55 PM

I have been using plaster batts for a long time. I made them with #1 Pottery plaster and springform cake pan rings. I have yet to have any blowouts from plaster getting in the clay, and don't find them fragile. I really like them for wide base platters.

I don't have pin holes in any of my batts, if you need them to have holes for wheelhead pins I have read that you can make them by putting a short piece of plastic tubing (like for aquariums) over the pins on the wheelhead and cast directly on the wheel. If you do it this way the tubing supposedly stays with the batt so the holes are less likely to get loose. I have also used a giant embroidery hoop for my really big batts and cast them on a counter top without the pinholes.

If you don't need batt pin holes plaster batts stay firmly in place with the Xiem Batt Mate.

edit: I have also seen a potter use a giffen grip to hold the batt on the wheel head. This would be useful if you take the pot of the wheel then need to put it back on again with less time spent centering it.

#61027 What Is The Most Dangerous Thing In Your Studio?

Posted by Min on 17 June 2014 - 03:18 PM

Agree with "Me" being the biggest danger. Lifting with my back and not my legs. We all know better but it's so easy to lift 50lb boxes of clay the wrong way. 

#59731 Keeping Carbon Transfer Lines Covered.

Posted by Min on 01 June 2014 - 10:11 AM

Some carbon / graphite paper has wax and or other binders, sounds like the one you are using does and it's acting as a resist to the glaze. Look for a wax and binder free transfer paper like this one: http://www.dickblick...transfer-paper/


It you use one of the coloured ones I would test it to check no colour is left after firing. 

#59210 Single Fire A Sculpture

Posted by Min on 25 May 2014 - 10:39 AM

Nice work! As Benzine and Colby have said go really slow and long for the preheat, 10 hrs like Colby said would be a good idea. If you have fired similar sculptures with similar thicknesses with the slow ramp it might be okay. Would be safer to put in your own ramp schedule so you know you are going slow enough through critical temps. The grog will help it from cracking, the lines that go through might be the weak spot.


If you don't have a slab to fire it on I would put a layer of grog or silica sand down on the shelf for it to sit on. Works like little ball bearings so the piece can move more freely as it shrinks in the kiln.


My comment about a clay being labeled at mature through ^05 - ^6, it was the word "mature" that I had a problem with. Just can't be mature at earthenware temps if it can go to stoneware temps. Doesn't matter at all for sculpture, just functional stuff.


Be nice to see your sculpture when finished and lit up.


edit: If I was firing this I would use this type of schedule:


ramp1 / 25F hr / to 190F / hold 10 hrs.

ramp2 / 75F hr / to 1300F / 0 hold

ramp3 / 250 hr / to 2170 / 10 minute hold * keep an eye on a witness cone to determine hold time to bring ^5 down.

kiln off.

If the pieces were thicker than they are for this sculpture I would slow the cool down also as follows:

ramp4 / 9999 / 1300 / 0 hold

ramp5 / 150 / 1000 / 0 hold

kiln off.

#59179 Single Fire A Sculpture

Posted by Min on 24 May 2014 - 05:13 PM

Hi and welcome.


Might be an idea to give some more info re sculpture thickness and if there is grog or sand in the body. A picture would help give an idea of how tricky it would be to fire. Sometimes a slab of the same type clay used underneath the piece(s) is a big help so it shrinks at the same rate as the sculpture, other times a thin layer of grog or silica sand or coils of clay is enough. 


Probably be wise to fire it slowly up to approx 190F and hold it there, depends on how thick it is as to how long, but at least for several hours. The preset slow ramp isn't going to be slow enough or hold at below boiling temp long enough, you will need to put in a firing program. Sometimes the fumes from a bisque will discolour glazes, would there be glazed pieces in the same kiln firing? If you do it slow I don't see a problem with single firing unglazed work.


BTW you said that the clay "matures at the range of cone 05 to 6", not possible. At ^05 it will be underfired and porous if it can go to ^6 and not be overfired.

#59148 Going Shopping

Posted by Min on 24 May 2014 - 11:01 AM

Things that I'd like to get at this point:

Sherrill Mud Tools, I'm a big fan of their ribs, and they have some nice looking sponges, and various other tools that interest me.




Plus one for the Sherrill ribs. I bought one of their white finishing sponges.  I saw a picture of someone using it in place of a chamois for finishing a rim. Doesn't work for me, it's way to thick. 

#58766 Remembering Your Mentors

Posted by Min on 18 May 2014 - 01:57 PM

 where full of ceramic energy and ready to pass on what they learned.




This is what I meant when I said that you (and many many others) are acting in a mentoring role on these forums. Not a face to face or one on one mentor / mentee relationship in the traditional sense of the word but one nonetheless. If we wanted just technical information that is readily available online, these forums also provide the encouragement and dogged determination that is so necessary in this field that is strewn with pitfalls.