Cress FX 23P Operation

[Elsa]

First post to this website because I can’t seem to find the answers I’m looking for anywhere else. I’ve read every finely printed online manual but it’s all very vague. 
I recently received a Cress Kiln. I understand how the kiln sitter works. I understand using cones. What I’m not getting enough information on is how long I’m suppose to set my timer and what I’m suppose to turn the thumb dial to. It goes from 0-10. The lower the number the lower it heats? How does that work when I need it to fire to a specific temperature? Also if I’m trying to start low then adjust to medium, then high, what am I moving the dial to? I have to test fire it with the new kiln furniture I have before I feel confident in running it with pottery and I’m feeling a little lost. I have an 04 for bisque fire and cone 6 for glaze fire. 
 

Everyone seems so helpful here I figured I couldn’t go wrong asking!

[Bill Kielb]

The timer is simply a countdown timer from ten hours to zero and is a backup fail safe device to make sure the kiln shuts off. Traditionally it is set for a small amount of time greater than the expected firing time. So if one expects the firing to end at 7 hours then the timer is set at seven hours thirty minutes.  Now for the hard part, one needs to learn a little bit about firing schedules and controlling their kiln, assuming it has manual controls. What type of. Firing controls does it have?

This may help, although not the best explanation it should give you an idea. https://youtu.be/_K_Glhstc4Q

 

 

[neilestrick]

FX kiln manual HERE. It explains how to set the thumbwheel and Firemate speed control. Like Bill said, the timer on the Sitter should be set for about 1/2 hour longer than you expect the firing to take. You'll have to do a firing or two to figure that out.

[Elsa]

“The main consideration for firing speed is that you should not fire faster than the ware will absorb heat, and you should not cool faster than the ware will release heat. Firing and cooling rapidly will result in stressing and even cracking the ware due to uneven expansion. Very thick pieces, such as hand molded sculptures, require very slow heating and cooling. Set the speed control on “normal” or “A” for pieces made in molds, while a setting of "E" can be used for most handmade pieces. For very thick handmade pieces or for low temperature soaking of these pieces or porcelain, use the manual setting for soaking, then turn the speed control to "E" or slow speed when you want to proceed.”

 

I don’t have a A-E dial option. Only the 1-10 firing adjustment. 
I’ve seen other Cress Kilns that have a dial under the kiln sitter that will adjust the speed of the firing and I don’t have that on my kiln.
I was wondering if most of this would be trial and error, but was hoping that there’d be a little more guild lines. 

[neilestrick]

I'd try looking through some of the other manuals on the Cress website. Chances are you'll be able to find one that matches up with your kiln.

[Bill Kielb]

7 hours ago, Elsa said:

is how long I’m suppose to set my timer and what I’m suppose to turn the thumb dial to. It goes from 0-10.

Good to see your timer actually goes from 0 to 20

5 hours ago, Elsa said:

I was wondering if most of this would be trial and error, but was hoping that there’d be a little more guild lines. 

Yes it will be trial and error based upon when you turn the firing knob ( not the timer) from low to high and dependent on how fully your kiln is loaded.. As Neil mentioned other manuals might give some insight. As a general rule for most ordinary pottery glaze firings tend to go 7-9 hours and average 300-450 degrees per hour rate. For bisque fires 10-12 hours at an average rate of 200 degrees per hour. How long you bisque has a great impact on ensuring removal of all the organics.

Drying things off and removing liquid water usually is a very slow warming over 1, 2, 3 hours as needed or warm up the kiln to 180 degrees, turn off and let it sit overnight. Some strategy to warm up but not make it to boiling point so things dry gently and slowly. No steam.

As far as firing speed, manual kiln operators often after dry do something like:  turn to low for two hours, medium 2 hours, then high until off. Low medium and high being relative to the kiln, load size,and experience which might mean turn to dial indicated 1 for two hours, then 3 for two hours, then high or 10 and let it make temp. You will need to experiment and learn, but your general goal is to be 7-9 hours for glaze and 10-12 hours for bisque …….. eventually with experience it will be whatever has proven to give you the best looking results for your glazes, clay, throwing and artistic preference.

[Elsa]

I’m sorry I should have been more specific, yes the timer goes up to 20. It’s the thumb wheel for the temperature that goes to 10. 
Thank you for the help! I’ll have to fidget with it to see what works. I’ve also read to leave the kiln on low overnight with the lid open to candle. Would I achieve the same by only running it a few hours then turning it off?

[Bill Kielb]

5 hours ago, Elsa said:

Would I achieve the same by only running it a few hours then turning it off?

Turning it on low and leaving the kiln open may keep it below boiling, depends on the kiln and surroundings. Preheating it and then letting it sit overnight works for some folks as well and uses less electric.

In the end it’s whatever works best for you and allows you to heat up the pots gently over enough time for them to dry. Automatic kiln controls allow you to set a preheat cycle where the pots are heated slowly to about 180 degrees  and held there precisely. Using that method often it’s easy to say 1,2 or 3 hours is enough time. Other methods are usually figured out over time, so experience is a thing. The basic idea is heat them (gradually) some temperature less than boiling and they will dry reasonably fast with no risk of shattering later because of steam.

[Kate in Kentucky]

Hello! I'm so glad I found this conversation. I have the same kiln, acquired from the family of a deceased friend and fellow ceramist, and I'd like to start firing it.  Everything I'm reading about firing manual kilns assumes there are at least three dials that go from low to high - and that's what I fired in the past (20 years ago).  I understand about the timer, but if I want a slow bisque fire, to cone 04: I assume I'd set the Firemate speed control at the lowest seeting, but what do I do with the Thumbwheel?  Do I set both the Thumbwheel and speed control at a chosen setting for the whole firing...or do I slowly increase the speed? 

Did you fire yet, Elsa? If so, please share the schedule you used and the results. I hope to do my first test firing tomorrow. 

Thank you so much!

[Kate in Kentucky]

Oops. I just realized that this kiln doesn't have the Firemate speed control that mine has, so maybe you can't help me. I have read the Cress manual, found online, but I'm still unsure what to do with the thumbwheel and speed control. Thanks in advance for any advice!

 

[Elsa]

I haven’t fired yet! Still waiting on the kiln sitter cone holders that were missing from my kiln. Missing the firemate dial has definitely been the biggest setback. I can’t seem to find instructions on how to fire otherwise. But I’m happy to know now I just have to cross my fingers and see what happens. Apply the knowledge I have and hope for the best. At least I’m not scouring the internet anymore haha. 

[neilestrick]

@Elsa @Kate in Kentucky Cress used their thumbwheels on a lot of kilns, so it may take some digging through their website to find a manual that matches your kiln. It may even be one for a different model than you have. If you don't find one, I would call Cress.

[PeterH]

@Kate in Kentucky only

This report on somebody having trouble with a "stuck" thumb-wheel seems to provide some insight on how it's supposed to work (and how to try to unstick it)
https://www.yellowcottagestudios.com/manually-firing-my-cress-kiln/

Also this posting

I'm under the impression that when correctly setup the thumb-wheel turns automatically with a speed (or profile?) governed by the speed control.

[Callie Beller Diesel]

@Elsa @Kate in Kentucky

I’m so sorry I missed this thread! My son cracked his ankle the day this was posted, and I wasn’t watching this part of the forum as closely.

I have one of these that I’ve been firing for years. It’s a really weird steampunk setup, but I’m pretty happy with it for the most part. I wouldn’t recommend it to otherCanadians because of the difficulty getting parts and service, but when you figure it out, it’s a good piece of equipment. If you’re in the US, it shouldn’t be an issue.

The timer is a safety shutoff, in case your cone melts into place, and the lever that drops cone sitter weight gets stuck on the cone. It doesn’t happen very often but when it does, it’s epic. In a bad way. It’s only happened to me once in 25 years of making pots, and that was this spring, which is the only reason I even bring it up.

The thumbwheel is actually the intensity settings, like on the old kilns that just had low-medium-high rheostats. The Firemate controller is a little servo motor on a infinite switch similar to older stoves, and that controls how fast the kiln turns itself up on its own. It’s a really analog kiln controller. If you put the kiln on manual it won’t adjust itself up and, you can either just leave it on low for something like a drying soak before firing, or you can adjust it yourself.  If you start off the firing on 0 and 0, you get a really slow firing. If you start off on 0 for the thumbwheel and the speed on one of the middle, it goes faster, etc. The idea is that you can play around with intensity and time to get what you need for your glazes and clay. You can also adjust the dials mid firing if you need to.

My 7 cu ft number takes about 8-9 hours for a bisque on slow, depending on how tightly I have it packed. Because I use a red clay and bisque to 04, I want that slow speed on both firings, so I use the 0 and 0 setting. A cone 7 glaze hits top temperature in about 10-10.5 hours, again starting on slow and depending on pack. Soak time is extra. Your results may vary.

 

[Elsa]

That was very helpful, thank you! 
I found out that my kiln actually has a firemate. Yes I feel ridiculous, haha. In my defense I don’t have easy access to my kiln, not being able to hook it up where I live it’s been kept at a relatives house. But I searched it recently and for some reason the firemate is attached to the side of the kiln! Happy to use your advice when I fire!

[Karie]

I have an old Cress kiln sitter too, and I'm still so confused about the speed dial settings...do I put it on A,B,C,D, or E?  Different for glaze or bisque? E is the slowest speed...I was told by a ceramics teacher to just keep it on C for now, but the manual says something different--it says "normal" is A---so confusing because A is the fastest speed. It's an FX 23P model. Thanks for any help! 

[Elsa]

Hi, Karie! So what I’ve discovered in the last few months is that it is A LOT of experimentation. I was always looking for very specific answers that didn’t exist. But hopefully I can help give you some clarity. 
The letter dial is the speed of the heat. So if I’m starting off low firing (1 on the number dial) and I set it on E I’m going to have to leave it on low for a lot longer than if I have it on A because it will get up to temp faster. The reason you would want to do this is if you have a lot of thick hand sculptures.
What I’ve gathered is that A is used as a standard for pieces that are completely bone dry and thin, say pieces thrown on the wheel. So depending on what you load is how fast you want the kiln to heat. If it heats too fast you risk cracking your thicker pieces. 
Right now I’m firing my kiln on E for 12 hours + because I have a lot of hand built pieces. A few hours each on low, med, high (1,5,10)  for a bisque fire. 
I haven’t experimented very much with glaze firing but what I have done is set the kiln to A and fired for another 12 or so hours on low, med, high until the kiln sitter flicks off. You’d only want a slower speed fire if your experimenting with certain glaze techniques. 
 

Hopefully this is helpful! I’m 100% a beginner so follow with caution. These are the answers I was looking for before I started firing with this kiln. 

[Bill Kielb]

This may be of use as you experiment to get your timing. Most bisque firings in the 10-12 hour range are effective at burning out all the organics in most clays. So for a typical bisque firing to 04 I would initially target 10-12 hours. Glaze firings generally can go much faster with a timeframe of about 5 - 8 hours to cone 6. While none of these numbers are set in stone they represent an average of about 200 degrees per hour for bisque and say 300 - 500 degrees per hour for glaze which has proven pretty reasonable for normal wares.

[Callie Beller Diesel]

Hi @Karie and welcome to the forum!

First of all, your instructor is telling you to use a medium firing speed, and if that’s what’s making your work turn out how you want it to, there’s no reason to change it. If you’re having technical issues, then yes, your firing cycle can be a part of many problems and solutions. In the early stages of trying to figure out how to make and glaze work, adding firing cycles into the mix can make the learning curve disappointingly steep. Most teachers will simplify that part of the process so learners aren’t overwhelmed, and introduce more information when a problem needs solving or you want to try something that looks cool.

The Cress kilns are a little weird if you haven’t fired manually or are used to a computer controller, but I’ll try and explain the best I can.

The infinite switch/dial that can either have numbers or letters (mine has numbers) controls the speed of the firing by turning the thumbwheel up. It works off a little servo motor. 

The thumbwheel is what controls the intensity of the energy the elements put out by turning the relays on and off at timed intervals. That’s what that loud clicking sound is that’s more noticeable in the first part of the firing.  As the firing goes on and the thumbwheel turns up, the interval will get shorter and shorter until the elements are on full all the time. So if you set your infinite switch on E and your thumbwheel at 1, that’s the slowest firing you can do without interfering with it manually. You can introduce holds if you want by turning the infinite switch to manual for the desired amount of time at any point in the firing.

In the kiln manual where it talks about A (fastest) being “normal” they’re assuming the user is a hobbyist who is making slipcast ware or doll pieces. Those are typically a thin and uniform thickness, the kilns aren’t usually packed tightly, and the clays used aren’t as vulnerable to cracking in the kiln. Under those circumstances, a longer firing isn’t going to get you better results, so doing it quickly saves power. 

If you’re making anything that isn’t slipcast, your firing cycle is more of a concern. You want to be able to adjust your firing cycle according to what you’re trying to accomplish, which is why there isn’t a super simple if this then that formula, or a one size fits all solution. 

Some reasons you might want a slower firing, or slow down parts of a firing:

Burning off extra impurities in the bisque fire (red or black clays), burning off impurities in the glaze fire (glaze recipe with lots of carbonates that cause pinholing), glaze soaking times to get desired results, soak times at the start of a bisque to allow ware to dry esp in humid climates, thick ware that needs more time to heat evenly, densely packed kilns that need more time to heat evenly, slowing down through the quartz inversion stages, holds at assorted points for fancy macrocrystalline glazes.

Some reasons you might want a faster firing cycle:

Energy savings, working with lustres, firing cycles where you’re avoiding glaze crystallization, certain glass firings that I wouldn’t attempt without a good pyrometer. 

These lists aren’t exhaustive, they’re just a few common ones.

To expand a little on what Bill said about firing times, a bunch of that is going to depend on the size of your kiln load. Using the slowest settings on that Cress system, my 8 cubic foot model takes 9.5 hours to hit a cone 04 bisque when densely packed with red stoneware pots that I sell for a living. I live somewhere really dry, so I don’t need a preheat. My glaze fire to a hot cone 7 usually takes 11 hours, plus a one hour cool down and a 15-20 minute soak hold. I would expect a 3 cubic foot model to hit that bisque in a shorter timeframe, and my glaze cycle has obviously been adjusted for my work, so may not be the best indicator for you.

 

[JohnnyK]

Something nobody has mentioned here is the use of a simple thermocouple thermometer (Digital 2 Channels K-Type Thermometer w/ 4 Thermocouples (Wired & Stainless Steel), -50~1300°C (-58~2372°F) Handheld Desktop High Temperature Kelvin Scale Dual Measurement Meter Sensor: AmazonSmile: Industrial & Scientific) which will enable you to tell exactly what temperature is inside the kiln. All it would take is drilling a hole near the center of the kiln making sure you miss the heating element and inserting the thermocouple. It will obviously take some practice adjusting the wheel and setting it for periods of time commensurate with the specific type of firing you are doing, but with practice, you should be able to develop your own firing schedules...

[Hulk]

Aye that. Add k type probe (with ceramic sleeve parts and ceramic plate on the back end), e.g.

 

...from there, take notes - time, temp, settings, results, observations - which may come in handy down the line, and place cones on each shelf...