Small loads in Kiln

[Claybottress]

I am new to owning a kiln. I have enough work to fire my first bisque, and am just waiting for a few more pieces to dry enough. My question is, do any of you ever fire your kiln less than full? I would love to run some smaller tests, but I hear it's not a good practice. Would love to hear what others think.

[liambesaw]

You can, just keep in mind you're wasting electricity or fuel, putting the same wear on the elements as a full load.  And the kiln may not fire as evenly.  But I totally understand wanting to try out your new kiln and the excitement that comes along with that!  I don't think a cheat once in a while will hurt anything

[Callie Beller Diesel]

If you have to do it, cluster your work near the thermocouple or the kiln sitter.  For instance if the thermocouple is roughly in the middle of the kiln, leave the bottom and the top shelves empty and fill the middle shelf. That way the sensor and the work are all getting the same amount of heat.  It’s what I do for my decal fires.

[Hulk]

I'm still working on culling green ware before firing. There's enough for a bisque load now; am expecting to toss about at least every third to reclaim, if not more. As for dry enough, if close to dry, I'm loading 'em up, as I'm ramping up to 200F the night before and leaving the vent running - plenty dry by next morning.

[neilestrick]

11 minutes ago, Callie Beller Diesel said:

If you have to do it, cluster your work near the thermocouple or the kiln sitter.  For instance if the thermocouple is roughly in the middle of the kiln, leave the bottom and the top shelves empty and fill the middle shelf. That way the sensor and the work are all getting the same amount of heat.  It’s what I do for my decal fires.

If you have a kiln sitter or single thermocouple this can work. If you have a kiln with multiple zones/thermocouples, or you have more work than you can cluster in a small area, then spread it out evenly throughout the kiln.

[Bill Kielb]

2 hours ago, Claybottress said:

I am new to owning a kiln. I have enough work to fire my first bisque, and am just waiting for a few more pieces to dry enough. My question is, do any of you ever fire your kiln less than full? I would love to run some smaller tests, but I hear it's not a good practice. Would love to hear what others think.

Everything above is good but I’ll just add if you heat a very full kiln it will take more energy than a sparsely filled kiln. No revelation there, right. Something to stay cognizant about, if you used a bunch of shelves and furniture but very few wares now you are actually spending your money to heat shelves ......... which usually look the same at the end of your firing.  They are still ugly shelves. So light loading and some equal conservative approach to the furniture you put in . If your furniture outweighs the wares then your paying mainly to  fire shelves. 

[liambesaw]

28 minutes ago, Bill Kielb said:

Everything above is good but I’ll just add if you heat a very full kiln it will take more energy than a sparsely filled kiln. No revelation there, right. Something to stay cognizant about, if you used a bunch of shelves and furniture but very few wares now you are actually spending your money to heat shelves ......... which usually look the same at the end of your firing.  They are still ugly shelves. So light loading and some equal conservative approach to the furniture you put in . If your furniture outweighs the wares then your paying mainly to  fire shelves. 

But the energy cost per item is still higher isn't it?  Will take less energy to hear a sparsely loaded kiln, but if the kiln bricks and furniture weigh more than the things you load, you're losing a lot of energy just heating the kiln up?

[Bill Kielb]

34 minutes ago, liambesaw said:

But the energy cost per item is still higher isn't it?  Will take less energy to hear a sparsely loaded kiln, but if the kiln bricks and furniture weigh more than the things you load, you're losing a lot of energy just heating the kiln up?

Yep, heating the kiln mass is constant so your controllable is the shelves. The heat needed is mass of kiln + mass of shelves + mass of wares + radiant and conductive shell losses. So Yep the kiln mass is the argument against multiple firings, or why per ware, multiple firings cost more than single heavily loaded firing.

It is interesting in that heavily loaded firings take more time therefore more energy but because of the more time part more shell losses also. So a bit non intuitive till ya think about it. Best observation to ponder, the shelves often weigh up to as much as the wares. Yikes, pure waste, each and every firing. Bad for Mother Earth one firing at a time.

[markalolo]

Take advantage of your light load to fire your kiln wash onto your shelves. The wash I’m currently using suggests firing the shelves unloaded before firing with glaze. 

[Claybottress]

Great suggestion! Thank you!

[neilestrick]

12 hours ago, markalolo said:

Take advantage of your light load to fire your kiln wash onto your shelves. The wash I’m currently using suggests firing the shelves unloaded before firing with glaze. 

The only benefit to pre-firing wash is a slight increase in durability. But as long as you're not sliding your pots across the wash it won't matter. Save the energy and just use them right after applying wash.

[Pres]

I fire manually, and have a sectional kiln. If I have good elements, I can usually use two sections tw reach ^6. So firing is not a problem for a light load. . just takes a little longer. I also use visible heat temperature of the kiln to tell me when I am nearing key points in the firing such as 1100F. 2000F. etc. A good heat/temp visibility chart will help you quite a bit. Heck, I can often tell how my firing is going at night by just looking out the kitchen back door window to the shop window. . I can see a thin line of glow from the lid other kiln on the white walls, When it is yellow white, I had better be awake!

 

 

best,

Pres

[Stephen]

On 4/16/2020 at 4:08 PM, Claybottress said:

but I hear it's not a good practice

I wouldn't say it's a bad practice or even a bad decision. It's just a decision. It's cheap to fire an electric kiln for me where I am at and I personally don't blink at firing a half load if I need to. My partner hates to do it but she's cheap 

Yeah it cost maybe a bit more per pot but its still cheap.

If I were you I would just take this opportunity to get your electric bill out and using the link below try to figure out just how much it cost you to fire your kiln. You can probably get to a pretty good guesstimate on electricity and  then add in that you will likely need a set of elements every couple hundred firings and the kiln itself will eventually wear out so I guess there is that ( but I have no idea when that would be, 1000 firings? 1500? maybe 2000 )

For example; one of my kilns is a Skutt 7cf and I know this one cost me about $8 on average in elect  to fire a load based on my energy cost and a set of elements cost around $350 and I'll peg kiln at 2000 firings so I'm going to say it cost me around $11-12 total to fire a load or about twenty-five cents a pot at 50 pots per load x2. (note bisque load holds more pots than glaze so that parts a bit wonky but the glaze fires hotter thus a bit more cost, averages close enough for me). 

Here is a pretty good link that might help on electric:
https://www.artclayworld.com/v/vspfiles/assets/Tips&Techniques/KilnFiringCosts.pdf

[Claybottress]

Wow. Very good insight. I am not concerned about the cost. I am so new, I just didn't know what the drawbacks were. It sounds like it might not be as accurate as a full kiln, which is a consideration if you are running tests and basing future firings on the results. I have a full kiln now, so no worries this time. But I want to add some touches in gold luster, and that will be less full as it's not on all pieces. So appreciate your time, and everyone else's here!

[neilestrick]

Digital kilns increase temp by cycling the elements on and off. A rough estimate is to say the kiln is on 25% of the time for the first 1/4 of the firing, 50% of the time for the second quarter, 75% for the third, and 100% for the last 1/4 of the firing. That averages out to 62.5% of the time. So take the kilowatts of your kiln, the total hours of the firing, and your cost per kilowatt hour and math it out. For a 10 hour firing in a KM1027 or e23T-3, with a cost of 15 cents per kW/hour:

10 hours x 11.5kW x .15 x .625 = $10.78 per firing. Controlled coolings are hard to figure into the calculations, but figure $1-2 for that. This formula should get your within a dollar or two, though. Some of the old Orton controllers will calculate this for you, and all of the new touchscreen controllers on the market will do it.

[Claybottress]

I want to thank everyone here! My first-ever kiln load by myself and fire went without a hitch. One little chip on the bottom of one vase, but given I fired about 40 pieces,  I'm very relieved. The witness cones melted as advertised, and every baby lived! Grateful to this resource and to all who commented.