Jump to content
Sign in to follow this  
yarddog

Firing Schedule, Cone 6 Glazes

Recommended Posts

neilestrick    1,381

I should go back to bed today. Seems that 570 per hour is shown in my L&L manual, too, for the first ramp in a Fast Glaze profile. I must have been thinking fast bisque or something. I had it in my head that the Fast Glaze profile went around 350-400F/hr. My bad. The fast Bisque profile is quite different, going slow at the start, slowing for quartz inversion, and slowing again at the end. So ignore everything I say today.

Share this post


Link to post
Share on other sites
MichaelP    21

My last post in that thread has a question still waiting for an answer:

 

+++++++++++++++++++++++++++++

 

We use Witgert Nr 11 clay. (max firing at 1300°C) <- How do you translate this to cone-speak?

With a chemical composition:

SiO2   73.4

Al2O3 21.6

TiO2   1.2

Fe2O3 1.0

CaO    0.1

MgO    0.3

Na2O   0.1

K2O     2.3

 

 

 

 

This question cannot be answered (unless somebody wants to test the clay or knows one with the same composition).

 

I strongly suspect that in Europe they use a standard for the final heating rate, so they can skip it and mention just the peak temperature.

 

For example, if we make it a standard to keep the rate of 60 C/h for the last 2 hours of heating, we could say that 1300C clay is a Cone 11 1/2 clay.  If the standard were 150C/h, then the same clay should be called (roughly) Cone 10 clay.

Share this post


Link to post
Share on other sites
neilestrick    1,381

The Cress Medium-Slow has a starting ramp of 400F/hr, which I think is too fast for a bisque firing in my opinion. It does not match up to the Bartlett Fast Bisque, which starts at 120F/hr, which is a much smarter way to bisque fire. The Bartlett bisque programs are about 2 hours slower. The Bartlett Slow Glaze also goes slower for the first 250 degrees, which allows for thew are to dry out after glazing. The Bartlett profiles also generally go slower at the end, which is good for glaze melt. The profiles in L&L are identical to the Bartlett V6CF. I think the Cress firing profiles are riskier, especially for bisque firing.

 

Per our earlier conversation regarding how fast kilns can actually fire, I think it's crazy that they put ramp numbers like 600F and 570F into the profiles at temps beyond 1500 degrees, as most kilns can't keep up with it anyway. I don't know of a regular electric kiln that can fire to cone 8 in 3.6 hours loaded with pots! They do all have disclaimers that firing times may vary depending on loads, etc, but I think it's unfair to make customers think they can fire that fast based on a programmed firing profile.

Share this post


Link to post
Share on other sites
MichaelP    21

Norm,

 

Helpful info. Thank you.

 

One small correction: the kiln power per cu.ft. you gave should be in kilowatts, not watts. :) 10 kWt/cu.ft, 6.8 kWt/cu.ft, etc.

 

Mike

Share this post


Link to post
Share on other sites
neilestrick    1,381

 

I worked with an actual engineer at Cress. They have extensive documentation of what percentage of time the E23 power relays are on at each speed, which rises as the temperature increases.  This i turn tells you how much wattage is being used.  I validated some of their detailed documentation with a stop watch.

 

But for us, the better validation is I can add up the predicted electrical use of all of our firings on my Excel Kiln Log and predict our monthly electrical usage on our digital power meter with less than a 4% error.  I have a really good handle on firing costs with this kiln.

Norm, how did you calculate your firing costs? Were you able to put a meter on the kiln?

 

 

 Nice. I've done some calculations as well to give me a somewhat accurate ballpark figure, but I would love to put an actual meter on my large kiln. It's firing times can very quite a bit depending on the density of the load, since it holds so much work.

Share this post


Link to post
Share on other sites
Norm Stuart    80

The Bartlett spreadsheet is terrific for a standard V6-CF controller.

 

Many of the kiln manufacturers have paid Bartlett to "customize" their V6-CF with: added speeds; different ramp profiles; and always a difference face-plate with the Kiln Maker's name replacing any reference to Bartlett.  Personally I wish I had a standard V6-CF as it's much better documented and is already updated with more advanced capabilities. So this spreadsheet won't exactly match the ramp schedule in every "customized" version. But it's a good starting point and I saved a copy - thanks!

 

Personally, I think people who don't spend the extra $100 a cone-fire controller costs will regret it for the life of their kiln.  What's so wonderful about programming in each ramp step for every single firing?  Some imagine this gives them "more control", but after I validated our cone-fire with Witness Cones (freakishly always exactly one cone too hot) I've never used a custom program apart from programming the Slow-Cool Ramp differently over time.  A cone-fire controller lets you program your own ramps, if you ever need to, but I haven't found the need.

 

All of the interesting things which happen with glazes occur after  the cone-fire program has finished.  A pre-heat, slow-cool, temperature hold, or delayed-start are all separate options to be added to a basic cone-fire program.

 

Here is a spread sheet, that calculates different firing profiles for kilns/controllers sold in US

http://www.bartinst.com/KILN/firingprofiles.xls‎

Share this post


Link to post
Share on other sites
Mart    23

Nice. I've done some calculations as well to give me a somewhat accurate ballpark figure, but I would love to put an actual meter on my large kiln. It's firing times can very quite a bit depending on the density of the load, since it holds so much work.

(answer comes after the quote) <- Mr Stuart, this is for you ;)

 

We have a small simple 3 phase electricity meter placed only for the kiln. Really easy to do (if you are an electrician) and eliminates the need for guessing.

 

We always write down the start and stop number from the meter and the controller programme number to our fifing log. Thanks to this, we know exactly what is going on.

I used to write down the liters of the load too but it made very little difference so I stopped (unless we fire stuff for someone else).

If we test new firing schedules, I usulay make a time-laps video of the controller read out, so we know what was actually happening. (webcam taking a picture once a minute, with a timestamp)

 

If you are going to buy a controller, get a one that gives you more flexibility (like Bentrup TC88). You never know, what you are going to fire one day. It's nice to have start delay, 9 ramps per program etc...

Share this post


Link to post
Share on other sites
neilestrick    1,381

 

Nice. I've done some calculations as well to give me a somewhat accurate ballpark figure, but I would love to put an actual meter on my large kiln. It's firing times can very quite a bit depending on the density of the load, since it holds so much work.

(answer comes after the quote) <- Mr Stuart, this is for you ;)

 

We have a small simple 3 phase electricity meter placed only for the kiln. Really easy to do (if you are an electrician) and eliminates the need for guessing.

 

We always write down the start and stop number from the meter and the controller programme number to our fifing log. Thanks to this, we know exactly what is going on.

I used to write down the liters of the load too but it made very little difference so I stopped (unless we fire stuff for someone else).

If we test new firing schedules, I usulay make a time-laps video of the controller read out, so we know what was actually happening. (webcam taking a picture once a minute, with a timestamp)

 

If you are going to buy a controller, get a one that gives you more flexibility (like Bentrup TC88). You never know, what you are going to fire one day. It's nice to have start delay, 9 ramps per program etc...

 

 

The Bartlett V6-CF has 8 segment custom programs, delayed start and preheat functions. It also allows you to combine a Cone-Fire with a Ramp-Hold, which is great for cooling cycles with multiple steps.

Share this post


Link to post
Share on other sites
Norm Stuart    80

Bartlett has an update for the standard V6-CF which changes each of the six custom programs to 16 steps from 8 step.  By combining User-5 and User-6 you have a 32 step program - which is more than I could imagine using. 

 

Simply send your V6-CF controller back to Bartlett to have the chip be flashed.  They're very helpful. http://www.bartinst.com/contact.html

 

However, until each kiln manufacturer pays to have their "customized" V6-CF program upgraded, customized versions will not have an upgraded version they can be flashed with.  So customized versions will continue to be 8 step programs with one 16 step custom program by combining User-5 and User-6.  When using a Cone-Fire, User-6 is the 8 step Slow-cooling program - but get it flashed with the update and you have a 16 step Slow-cooling program.

 

 

If you are going to buy a controller, get a one that gives you more flexibility (like Bentrup TC88). You never know, what you are going to fire one day. It's nice to have start delay, 9 ramps per program etc...

 

 

The Bartlett V6-CF has 8 segment custom programs, delayed start and preheat functions. It also allows you to combine a Cone-Fire with a Ramp-Hold, which is great for cooling cycles with multiple steps.

 

Share this post


Link to post
Share on other sites
neilestrick    1,381

 

Bartlett has an update for the standard V6-CF which changes each of the six custom programs to 16 steps from 8 step.  By combining User-5 and User-6 you have a 32 step program - which is more than I could imagine using. 

 

Simply send your V6-CF controller back to Bartlett to have the chip be flashed.  They're very helpful. http://www.bartinst.com/contact.html

 

However, until each kiln manufacturer pays to have their "customized" V6-CF program upgraded, customized versions will not have an upgraded version they can be flashed with.  So customized versions will continue to be 8 step programs with one 16 step custom program by combining User-5 and User-6.  When using a Cone-Fire, User-6 is the 8 step Slow-cooling program - but get it flashed with the update and you have a 16 step Slow-cooling program.

 

 

If you are going to buy a controller, get a one that gives you more flexibility (like Bentrup TC88). You never know, what you are going to fire one day. It's nice to have start delay, 9 ramps per program etc...

 

 

The Bartlett V6-CF has 8 segment custom programs, delayed start and preheat functions. It also allows you to combine a Cone-Fire with a Ramp-Hold, which is great for cooling cycles with multiple steps.

 

 

 

If firing ever gets so complicated that I need 32 steps, I'm going to quit! :wacko:

Share this post


Link to post
Share on other sites

Darrel,

 

Could you please tell us how long it takes your kilns to get to a certain cone (let's say, Cone 6), and how quickly the temperature drops to 1400F when you cool them naturally?

 

Do you use matte and crystalline glazes?

 

Thank you.

 

Mike

 

Mike, 

My kiln usually takes about 6-10 hours to get to cone 6 depending on what time of year I fire (My kiln is in an outdoor structure, and it takes a while to fire in the middle of a blizzard). I do not track cooling very throughly, but I know it takes about 11 hours to cool to under 100 degrees. I occasionally use a couple matte glazes, but I have not tried crystalline yet. I want to.

 

Sorry I couldn't fully answer your question.

 

Darrel

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
Sign in to follow this  

×