Fire and snow.

Heavy snowfall tuesday. Spent the day on another 6.5 hour quickfire of the kiln. Salt glazed the last hour and half. Very good day watching the snow fall while gathering firewood and stoking the kiln.

I am very excited about the heat this firebox can generate in the small chamber.

I actually have to hold back on stoking speed sometimes. Thats still a new one for me.

And it can make alot of really black smoke if I put to much in to fast.

When I start in the morning, I use a kerosene heater in the barn for warmth. But after about an hour, the heat off the kiln becomes plenty in itself. So I turn off the heater for the rest of the day.

There were two pots on the left from the last firing that I refired to get a better glaze effect. I put in a few tiles too. They came out nice.

I liked this pot and plate.

Pottery photos from latest wood kiln firing.

Here are the pots from the latest firing. My focus has been on improving my firing to a useful level where the resulting pots would be glazed fully. That is now possible. My next effort will be to improve the shape and style of the pottery to a more pleasing and useful level. The shapes may be crude, but the salt glaze is really getting close. Im excited like a little kid!


The darker pots are that way because of the naturally dug Cutler clay they are made of. There is a low percentage of glass dust in these.

This next little pot with a handle is made from Flora dug clay that has a slightly higher glass dust content than the ones above. It cracked becase it dryed out too fast in an earlier bisque firing.

The next ones are all Flora dug clay with a near 50 percent addition of bottle glass dust.

These are the two that were nearest the firebox flue. The heat was too much for them. I think that the high level of glass dust in them made the melting point lower for them. I think from now on I will either fire entirely one type of clay mix or the other. No more mixing the types in a single firing. Its too hard to comprimise between them on the firing needs. Obviously the higher glass dust clay bodies need a lower temp or shorter firing time than the near pure clay bodies do.

Heres a cool before and after photo set from the kiln to compare.

Huge success with pottery kiln modifications.

My kiln rebuild was the best thing I could have done. I am starting to realize just how gentle the balance is during a firing. All the variables have to be addressed and satisfied in order to create the best possible conditions for the fire to thrive. Expert I am not, but I am gaining on understanding how it works.

From what I can tell so far, I have gained alot on maximum temperature. I actually melted at least one pot into dripping gooo! I for the first time used cones. Not the correct ones, but close enough to get an idea. I bought an odd assortment of cones from ebay. I placed an 017, 016 , and a 6 near the spy brick. The 017 went first, then the 016. Then finally the 6 bent over. I melted all of them by the time I was ready to finish stoking the firebox. My pyrometer thermocouple is used and abused. It reported around 2000' deg F then failed. Then my front most pot in the chamber near the firebox flue started sagging down!

I thru a steel fitting into the ware chamber to see if it would melt. It glowed but didnt melt.

Notice the color progression from orange to yellow! Getting hotter.

Look at the clay gooo dripping down into the firebox from the chamber above.

Wood kiln modifications to add crossdraft flame flow done.

Its been below freezing since Christmas here, so the snow and ice have built up alot outside. Though cold its beautiful too. Looking out my back door across the porch and backyard to the kiln barn.

I reworked the kiln chamber floor as best as I can to reflect Peters crossdraft suggestions. Im still thinking of ways to improve my ash pit which is undersized and difficuct to empty. The entrance flue vent to the chamber is now at the front while the exit flue to the chimney is at the rear.

Looking foward to trying this out as soon as I get the needed firewood gathered up!

Kiln science and improvements

A fellow blogger which I discovered searching over the internet on kilns a while back replyed to my open request for suggestions on my kiln. Peter shares a strong interest in wood kiln building and has inspired me to test the limits of my abilities. Thank you for sharing!

from Peter:

Hi Richard,

Attached should be your drawing of your kiln with modifications to the firebox. I probably haven't given enough detail in my modifications to show you all that clearly what could be done, but thought thisshould give you an overview of the sort of thing that you might attempt to sort out the problem. Not sure if the modification I suggest here would be possible with the current structure of your kiln, but do let me know what you think thus far.
There are other ways to go with this too. Turning it into an updraft could be easier to do. If you can put a hole through the top of the arch without causing it to become unstable, a length of pipe put above that for a chimney could result in a useful little kiln. Another way would be to rebuild the chimney alongside the chamber and feed into it from near the top of the chamber arch. This would also make a form of updraft kiln, but you would also have the benefit of being able to have an effective chimney damper built into the chimney above chamber height which would give more control than usual in an updraft kiln.

My bottle shaped updraft kiln will reach in excess of 2192 Fahrenheitin the lower hotter part of the kiln in about 5.5 hours. I recently read of a small round updraft kiln that would get to cone10 (about 2336 F) in 3.5 hours with wood stoking and natural draft (noblower).

Anyway, do keep in touch Best Wishes,

Peter

I cant wait to get to work on the modifications. Thank you very much!

Here are my possible modifications to the kiln firebox.

I am limited with my useable floorspace in front of my kiln so I am restricted to the footprint the kiln now sits on. I also have a low roofline above the kiln. I see how the firebox can be moved so as to give a cross-draft effect. I will have to see if it can be done. Thanks again for the input!

Diagram of my kiln flame path

Here is a picture of how I see the flame and hot gas flow in my flora kiln. Notice the pottery in the areas that achieve the salt glaze are highlighted in light blue. I am thinking of closing off the rear most firebox exit ducts into the ware chamber to force the hot gasses to travel across the lengths of pots more.
Any thought or suggestions are welcome. You may need to click on the picture to zoom in and see the details.

Salt glaze is a tricky thing!

Im pretty pleased with the pots and pieces near the flue. The salt worked its magic there. The front had almost no glaze effect. It may be that the chamber temps were lower at the front of the kiln. It may also be that most of the churning flames the salt vapors ride on were nearer the flue side. Either way it means I still havent mastered this yet. Back to the drawing board! Any suggestions? Im thinking of closing up the flueside chamber floor duct and expanding the frontside duct. My hope being that it will force the salt vapors to travel across all of the pots in the chamber, not just the rear most.

A two handled pot and a candlestick holder. I may put the holder back in one more time. Dont like the lack of glaze in the fluted areas.

I am now settled on some facts and limitations I have to abide by.

1. Creekbed clay is out for now as I cant reach the temps needed to flux it out. Nor does salt vapor seem to have any effect on it. Maybe the low iron oxide content in it.

2. Field clay from the Cutler - Burlington site has a high iron oxide content and salt glazes easy to a near black glaze.

3. Field clay from the Flora site has a somewhat lower iron content. It also has something else in it I havent identified that gives a grey green to it. It also salt glazes well if not quite as good as the other field clays.

4. I want to seperate the bottle glass I use as flux in the clay bodies by bottle colors. Dark browns, greens, and clears will be divided to help control the resulting colors in firing the clays.

Another first for me is that I logged time/temps this firing. I may be able to use this to work out some improvements in the kiln or my stoking methods.

I can say that I did use about 1/3 less wood this time than the last. It did come up to temp quicker as well. So closing off unused chamber space when firing a small load does have a positive time and fuel savings effect for my kiln.

First firing of the year.

I started about 9:30am and fired until 6:30pm. I cant wait to see how they turn out.

Heres an early pic with alot of steam flowing out. The pots were already dry, so all I can think of is the bricks I used to close off part of the chamber were damp. It burnt off and the temperature climbed after that.

And here is the pyrometer working its way up to temp. Still working out the best thermocouple placement to read from. Its doing better this time. I may buy a new K type one, the one I am using is a repaired one so I dont trust its accuracy to much.

I'll post pics soon of the results for you to see.

Thinking smaller, getting ready for next firing.

Here are a couple more photos of some of what came out of the Christmas firing of my kiln.
The bricks are really great. The white one in front is one of my favorites.

The large tiles came out very well also.

I went thru alot of firewood last time getting the kiln up to salt glazing temperature. In an expiremental effort to speed up the firing and save fuel, I am reducing the chamber size to salt glaze my pots. I will let you know the results soon.....

All bricked up, waiting for the mud to seal the cracks. I also moved the pyrometer thermacouple probe into the heart of the chamber this time. I hope to get a more accurate reading from it.

Firing is set for sometime this weekend.

Christmas firing challenge and success

I had been planning to fire up my kiln on Christmas day for a week now. I wasnt sure I was going to be able to stick with it after I injured myself on my left hand on Christmas eve. After a trip to the ER and 5 stiches later, I decided to very carefully go on ahead with the firing. With the help of my wife Jackie, my two sons William and Daniel, and their good friend Brandon, I was able to keep the firebox stoked the needed twelve hours. Even with the wind blowing and temps outside dropping into the upper 20s F they helped me with little complaint. Thanks to all of them for the hard work.

I realy like the salt glaze effect on this candlestick holder. Grey green maybe from the bottle glass dust mixed in with the local Flora clay I am using on these.

My chimney flame arrestor had been working great! No more visits from concerned neighbors or the local police over flames shooting out in full view. lol

I enjoyed using my newly purchased pyrometer off Ebay. I still need to discover the correct location in the chamber to place the thermocoule probe. I was getting readings from it far below the actual temps I knew I was reaching. I must of had it in a cold spot out of the main flow of heat. Better luck next time.

Tiles and bricks came out great! Only lost two tiles to cracks. the white brick and pots are from the streambed creek clay. The low iron content make salt glaze not work well at the temps I can reach. I had much better flow this time thru the chamber for the gases. I found that stacking the bricks longwise to the exit flue with 3/4 inch gaps works good. Much less smoke in the barn this time! I will try to post some more pics of what came out soon.