Babs

I rhink you inadvertently did a reduction firing. Easy to do in a small gas kiln.
Do you have time to refire one as a test making sure you have a  fully oxidised atmosphere? With that amount of copper I could get black pots without trying in my gas kiln if not careful re atmosphere.

I rhink you inadvertently did a reduction firing. Easy to do in a small gas kiln.
Do you have time to refire one as a test making sure you have a  fully oxidised atmosphere? With that amount of copper I could get black pots without trying in my gas kiln if not careful re atmosphere.

I rhink you inadvertently did a reduction firing. Easy to do in a small gas kiln.
Do you have time to refire one as a test making sure you have a  fully oxidised atmosphere? With that amount of copper I could get black pots without trying in my gas kiln if not careful re atmosphere.

I rhink you inadvertently did a reduction firing. Easy to do in a small gas kiln.
Do you have time to refire one as a test making sure you have a  fully oxidised atmosphere? With that amount of copper I could get black pots without trying in my gas kiln if not careful re atmosphere.

I rhink you inadvertently did a reduction firing. Easy to do in a small gas kiln.
Do you have time to refire one as a test making sure you have a  fully oxidised atmosphere? With that amount of copper I could get black pots without trying in my gas kiln if not careful re atmosphere.

Do you have a pyrometer to log your kiln progress through firing? 1 cone is not usual practice. A bank of 3 cones one below target cone , target cone and one above the target. A bank of cones on each shelf to see how the inside of  your kiln is behaving.
Good luck.

Do you have a pyrometer to log your kiln progress through firing? 1 cone is not usual practice. A bank of 3 cones one below target cone , target cone and one above the target. A bank of cones on each shelf to see how the inside of  your kiln is behaving.
Good luck.

I've used three potteries that had gas kilns inside. Good venting is a must. Unlike an electric kiln, a gas kiln can introduce deadly carbon monoxide into the space. A carbon monoxide sensor alarm is important. It also seems that the heat given off by a gas kiln is a lot higher than an electric kiln. For a gas kiln in a situation like yours, I would suggest putting it outside. I have a small gas kiln in my backyard that I cover with a tarp between firings (no shed). The only drawback to using a tarp is that I have to wait for a couple of days with no rain forecast so I can fire it, unload it, and cover it back up before any rain. I can get to cone 10 in six hours and let it cool overnight. It is a converted electric kiln that can be found by searching for: TDI downdraft kiln conversion 

@ByrdIf the cone bent, then it reached that cone. The potential problem is that it didn't spend enough time at high heat to adequately burn out all the organic matter, which could cause issues with your glazes. If you're using a white clay body, then it'll probably be fine. If you're using a brown body then it's more likely to be an issue.
HERE is a thread with a lot of good information about firing Duncan kilns and how to slow them down. If you use the search bar you'll find several other Duncan threads that may be of use to you.

What temp did it reach after the initial 2 hours?
It will be interesting to see how your pots fared.

Babs
Zinc is processed two ways: the French process and the American process. The American process is just simply “roasting” (we call it calcining) that removes impurities. It is denser because it typically 80% pure, with 20% of various minerals commonly associated with zinc. The French process involves vaporing zinc at higher temps, resulting in a purity above 99%. It is finer, with less density. The zinc you are looking for is called Maximo 910 in the States, unless it has been sold to another company yet again.
Tom

Thought this was a good time (seeing it is American Thanksgiving), to put out a thank you to the potters on this forum who give selflessly of their knowledge and time to help other potters.  Together you have built a great resource and you are very much appreciated.  
 

per Standard Clay
 

I don’t think the low fire firing will change it dimensionally a bunch. Can you repeat it but make a generous gallery so it will fit a wider range of opening?

Looks like one man's collection of other folk's glazes, prob no text book as such
Some are Bwenard Leach's , some are Val Cushings , you say they are your professor's so why not ask him?

Looks like one man's collection of other folk's glazes, prob no text book as such
Some are Bwenard Leach's , some are Val Cushings , you say they are your professor's so why not ask him?

Looks like one man's collection of other folk's glazes, prob no text book as such
Some are Bwenard Leach's , some are Val Cushings , you say they are your professor's so why not ask him?

Vivika simi matt is from Otto and Vivika Heno I think as I have thier glaze handout from a workshop years ago.The rest are unknown to me. Looks like one mans,womans glaze book collection he/she put together for a class

Looks like one man's collection of other folk's glazes, prob no text book as such
Some are Bwenard Leach's , some are Val Cushings , you say they are your professor's so why not ask him?

As a gas potter for 50 years I see the burner is pushed into the kiln  to far-needs to be away from kiln a bit and the air flaps are closed down to much (open them up)
these are the most obvious ,but kiln design and orifice size are also concerns -I can see the 1st two issues in your photos for sure so they are easy to fix.

Ifit was bisqued to a lower temp. it will take on more glaze if glazed as usual. Maybe test fire one glazed piece through a normal firing, place it on a clay biscuit to protect your shelf.

Ifit was bisqued to a lower temp. it will take on more glaze if glazed as usual. Maybe test fire one glazed piece through a normal firing, place it on a clay biscuit to protect your shelf.

As we have been drawn to working with our hands and clay i'd say our haptic sense is heightened. Certain pots will attract us, cupboard full of similar mugs, we'll find a favourite and seek it out.
Potting with eyes closed when centering and  pulling up clay can make our haptic sense reveal itself also.
It is cruel to go to an exhibition and be forbidden to pick up and touch the pots.
 

If the colour is the same in both (I'm guessing it is if you haven't noticed a difference) then put a drop of water on a piece that was for sure bisqued to 1860F and time how long it takes to soak into the clay. Repeat with the clay that was possibly only bisqued to 1200F and see if takes longer. You can also stick your tongue on both pieces, the lower fired one will stick more. (maybe don't do this in public)

Yeh well, aussie here, I built a vent above the stack and suspended a flue pipe  above the short stack with enough room to operate a damper. It reached up a few fluepipe lengths into the hood then to outside I was firing inside a shed so  needed to draw the fumes up into the hood a ways.
Fibre kiln. .fired fast up, (only used tge pilot lights for first couple of hours), and dropped down  very fast unless sorted.