Denver Kiln?

[Babette (Shawn)]

I have been offered a Denver KL-50DD 12 inch deep kiln, I believe it is all fiber top & sides and it looks very clean. I know nothing about these kilns, does anyone have experience good or bad please? The story is: last month I was driving down from Canada to California and I found a 2 year old-never-been-fired Glass Glow 350-16 fiber lid kiln for sale on Seattle's Craigslist. The kiln REALLY had never been fired and I could not pass up a good deal. Since I was driving a small Toyota the nice gentleman who sold the kiln to me delivered it to my friends glass studio in Olympia...now my friend wants to trade me her larger Denver kiln for it. I love the idea of a BIGGER kiln, but I am not familiar with the Denver Kiln company. The controller is their standard controller, I think. Are there tests one should run on a "used kiln" to make sure it is safe and up to speed? My friend had the Denver kiln built for her about 7 years ago but has not used it in a few years, it does look clean and well maintained.

[Bert Weiss]

In my opinion, Denver kilns are terribly under insulated and under built. They are cheap, but you may get less than you pay for. Glass Glow kilns are well built.

There is a theory that an under insulated kiln will cool faster, which is better. My kilns run MUCH cooler on the outside. I could place a paper bag full of styrofoam peanuts on top of my kiln, and they would not change state during a 1500ºF firing. Don't try this on a Denver. My kiln cools at a reasonable rate, much faster than an all brick kiln, which is an important consideration, when considering design factors.

[carol carson]

I have a Denver kiln for ten years now and still love it. It works great and I use it all the time. It cools down quite slowly. It has their standard controller on it, which is different from most others in that you must figure out your schedule in minutes rather then hours, so rather then put in 3 hrs, you punch in 180 minutes. Otherwise very easy. I think the choice is yours. I've heard good things about Glass Glow too.

[Valerie Adams]

So you've been given a free kiln with a retail price of about $3000, and it holds a 24" shelf.

You don't mention the size of the Denver...[edit: I can't believe I missed the Denver model number in your post! Still, while the size is wonderful, I'd probably stick with my original decision]

Things I'd have to consider, if this were my choice. How much studio room do I have? How often do I work larger than a 24" shelf allows? How much electricity does each kiln require (my breaker box is maxed, for instance). How patient am I to need to fill the larger kiln before running it, as opposed to wanting to fire only a piece or two? How much do new shelves cost (I like having several extras prepped and ready to go).

You're close to Phil, who built the Glass Glow, in the event you need service. The Denver is seven years old.

For me, the decision to stick with the new kiln would be a fairly easy one.

[Morganica]

Ironically enough, the 50DD is exactly the kiln I'm considering right now, with a few added elements, so take this with a grain of salt:

Expanding on what Val said...Your infrastructure needs to support it, which means you reconfigure a circuit for the extra amps required, and that you have adequate ventilation and storage/working space. A bigger kiln takes more than just its own physical space. It needs a fair amount of clearance around the kiln even when it's not running, and larger storage space near the kiln for the additional kiln furniture and supplies, and more storage/shelves for the increased number of glass projects waiting to go into the kiln.

If the bigger kiln doesn't draw more power than the one you have, take a close look at the elements--there may not be enough. Too-few elements means the kiln will take longer to heat that larger space evenly, and you may have issues with hot/cold spots.

The biggest deal, though, is that a bigger kiln is more expensive to run, not because of the cost of electricity but simply because it needs to be filled. This sounds silly, but the first time you look at a 12-inch plate sitting all by itself on that huge kilnshelf, you'll realize you're wasting a bunch of space. I tend to delay firing until I've filled the kiln, so I make each firing count--which means it takes longer to actually get a piece out of the kiln--or I simply make bigger stuff to begin with.

Bigger stuff means you're using more glass, so you tend to buy/use a lot more glass. If you're selling, that also means you must sell more to return that investment.

I'm not saying those are bad or insurmountable things, and if you really do plan to move to much bigger (and taller, since the 50DD is 18 inches deep) work...great. If you're not sure yet what you're going to do with all that space, I'm with Val--I'd think twice about dumping a new kiln for a 7-year old one. Can you support both kilns in your studio? That would probably be my choice...

[Valerie Adams]

...and think about why your friend wants the smaller kiln.

[Babette (Shawn)]

So you've been given a free kiln with a retail price of about $3000, and it holds a 24" shelf.

You don't mention the size of the Denver...

Things I'd have to consider, if this were my choice. How much studio room do I have? How often do I work larger than a 24" shelf allows? How much electricity does each kiln require (my breaker box is maxed, for instance). How patient am I to need to fill the larger kiln before running it, as opposed to wanting to fire only a piece or two? How much do new shelves cost (I like having several extras prepped and ready to go).

You're close to Phil, who built the Glass Glow, in the even you need service. The Denver is seven years old.

For me, the decision to stick with the new kiln would be a fairly easy one.

_________________________________________________________________________________________________________________________________

I did pay for the Glassglow Kiln, I bought it off of Craigslist for $1800 including quite a bit of glass & some useless molds...I thought it was a good deal so I had to buy it even though I swore to never do business with Glass Glow again (another story)

The inside dimension of the Denver is 42" x 28", so I am thinking it holds a 40" x 26" shelf? I also have a Paragon Ovation kiln that is shallow (11 inches deep) and holds a decagon shaped (ten-sided) 40" x 21" shelf...the Denver 40" x 26" four sided shelf is more practical. Why do they make those multi-sided kilns?

The size of the Denver is good for me in every way...I can handle the footprint and the electrical (I run my studio off of solar) The Denver has a fiber lid & sides and the Denver kiln comes with one large shelf which is good for me.

The Central factor for me is the reliability and sturdiness of the Denver Kiln? Am I foolishly trading in a newer Volvo for a used Chevy SUV? If I have a mechanical problem with the Denver what is it likely to be?

[Valerie Adams]

Jeez, I obviously needed more coffee when I posted this morning!

I remember your issues with Phil and understand your reservations. But those kilns have been on my wish list for awhile.

If you'll be keeping your Ovation, then you've already got a smaller kiln for when you want to do only a piece or two. I converted to solar a few years ago (runs my kilns and the house) but still would need to expand my breaker box for a larger kiln. If you've got that handled, that's great.

[Marty]

Re Denver- if you keep it dry and don't let your students near it without supervision, it's fine. I know people who have used Denver kilns for production work for years.

I just picked up a "free" Denver 60.The first thing I had to replace was the hinge because it was almost frozen with rust.
Then the lid's fiber board had to come out because it was sagging badly, which meant that the elements had to be removed first.
One of the mullite tubes needed replacing and the weird element support system was on its way out so I decided to go the quartz tube route.
Having pulled the refractory out of the lid, I found lots of rust inside so that will have to be cleaned up; maybe I'll paint the bare metal with a high temp paint to protect it. I'd considered an inner liner of thin sheet ss but the cost didn't make sense.
New blanket (1") and board (2 layers of 1" LD with staggered joins) will replace Denver's insulation.
The blanket on the sides was rusted and pulling away from the frame so that came out too. The rust needs the same treatment as the lid and the blanket will be replaced by unmortared brick on the flat (4" of insulation). I already had the brick.
The floor of the kiln was dry brick- that's been removed, the metal will get the same treatment for rust and the brick will be flipped over so the unused surface is now up.
I wanted this on casters so I had the frame cut down to accommodate the additional height of the wheels.

I'll be reusing the relays but replacing the 3 button controller with a GB1 that I already have. The 3 button will be used on that stoopid Evenheat tub.
If I had kept the controller (and had to buy brick and blanket), I'd figure my outlay at less than $800 and 2-3 days work for a kiln that will perform a lot better than the original.

One of the reasons I'm detailing all this is to encourage fusers to get to know their equipment. The kiln is simple, a toaster without the pop-up. All the info is available- I recommend starting with Henry Halem's Glass Notes.

[Valerie Adams]

One of the reasons I'm detailing all this is to encourage fusers to get to know their equipment. The kiln is simple, a toaster without the pop-up. All the info is available- I recommend starting with Henry Halem's Glass Notes.

I completely agree with Marty's statement. I'm not super skilled in home or kiln maintenance stuff but managed to single-handedly rescue one of my Paragon kilns after a severe meltdown. Common sense, a few basic tools, the internet, a little energy, and a few bucks restored my kiln. Here are a couple progress-photo posts:


http://valerieadamsglass.blogspot.com/2 ... chive.html

http://valerieadamsglass.blogspot.com/2 ... chive.html

[Babette (Shawn)]

Ok I have more info on the DENVER kiln I was thinking of trading for my Glassglow. This Denver kiln comes with a West 4400 1/4-DIN Setpoint programmer?, the controller came with the kiln from the Denver factory. The kiln is fiber both top and sides, it is 41 by 27 inches inside and 18 inches deep. It has side and top elements, the side elements are run on a separate manual controller. Is anyone familiar with the WEST controller? What would it take to put both the side and top elements on a one, new controller with a mercury relay, maybe an Orton? I had a run-away kiln last year so I am very concerned with safety.

[Rick Wilton]

If you are going to replace the controller go with SSR relays they are much better to use (imo). Mercury relays are illegal in California anyway.

a 1/4 din controller is a small usually 4 button controller likely not what you want to use to program a kiln. (it is however what I use)

Rewiring the kiln to a new controller that controls all the elements isn't that big of a deal, as long as you know what to do. It can be a challenge and expensive if you have to bring in an electrician to a) figure out what to do and how to do it b) to actually do the work.

[Al Bray]

What would it take to put both the side and top elements on a one, new controller with a mercury relay, maybe an Orton? I had a run-away kiln last year so I am very concerned with safety.

Swapping out the controller is definitely possible. As Rick mentioned, the cost/effort to do so is more of how much you are comfortably with taking on yourself vs having to reach out to someone or some company to provide a turn-key solution.

About 2 year ago I picked up a used Denver KL-50D being offerd for sale on ebay on the cheap. The kiln was one of several that a stained glass shop in the Chicago area had used to do a lot of custom glass bending to replace windows in many of the Arts & Craft style homes that were being renovated in the area. While the kiln was 12+ years old it was in remarkable condition due to the fact it rarely was fired above 1300 degrees. All the elements worked and fired evenly, no broke or cracked mullite element suspension tubes, no warping of the lid, very little rust. Just a bit of discoloration/fading of the exterior paint.

But it came without a controller as the seller was holding on to the Digitry that he used to control several other kilns.

This put me on a path to build my own controller. After a bit of research (surfing the web, Duralite, Joppa Glassworks, posts from various forums, reading Glass Notes, etc), again I turned to ebay and was able to pick up a Watlow F4S PID based controller, the appropriately power rated Watlow Din-A-Mite SCR power controller (solid state version of a mechanical relay), thermo couple /wiring/connectors, and enclosure to mount all the components into.

Out of pocket costs were about 1600.00 for the kiln and all the components to construct the controller and get it properly wired to the kiln.

There was a great deal of time spent learning. Not just about about the various aspects of temperature controllers but also about the various +/- of different kiln construction method/materials, +/- of different power control options (SCR, SSR, mechanical relays), and ways to gain better control over the firing profile to get a specific reproduceable result.

While at some point I may trade out the Denver, I doubt I will ever let the F4/Din-a-mite SCR controller combination go because of the features/control it gives one over the firing profile as well as the relative ease to adapt it to a different kiln environments and yet maintain the same firing profiles for a particular process.

As Marty stated, what I learned in the process of taking it on myself was way more valuable in moving me forward with my understanding of what is going on in the kiln than the new (to me) kiln or controller on their own.

Good luck in your pursuit in what ever direction you decide to move in!

- Al

[Bert Weiss]

But it came without a controller as the seller was holding on to the Digitry that he used to control several other kilns.

This put me on a path to build my own controller. After a bit of research (surfing the web, Duralite, Joppa Glassworks, posts from various forums, reading Glass Notes, etc), again I turned to ebay and was able to pick up a Watlow F4S PID based controller, the appropriately power rated Watlow Din-A-Mite SCR power controller (solid state version of a mechanical relay), thermo couple /wiring/connectors, and enclosure to mount all the components into.

Out of pocket costs were about 1600.00 for the kiln and all the components to construct the controller and get it properly wired to the kiln.

There was a great deal of time spent learning. Not just about about the various aspects of temperature controllers but also about the various +/- of different kiln construction method/materials, +/- of different power control options (SCR, SSR, mechanical relays), and ways to gain better control over firing profile to get a specific reproduceable result.

While at some point I may trade out the Denver, I doubt I will ever let the F4/Din-a-mite SCR controller combination go because of the features/control it gives one over the firing profile as well as the relative ease to adapt it to a different kiln environment and yet maintain the same firing profiles for a particular process.

As Marty stated, what I learned in the process of taking it on myself was way more valuable in moving me forward with my understanding of what is going on in the kiln than the new (to me) kiln or controllers on their own.

Good luck in your pursuit in what ever direction you decide to move in!

- Al

I heartily endorse Al's selection of control instruments. The controller and SCR can be often found used on Ebay and these instruments can last a very long time. I have had a set of used SCR's on my kilns for 15 years without a failure. I think the Watlow devices are a significant step up from Bartlett or Orton. Digitry is good, but can rarely be found for less than full price. The trick is that you have to learn what all the options are and then how to read a serial number to assure you are getting the model that will work on your system. SCR relays require a 4 - 20 milliamp output. Bartlett and Orton controllers do not offer this option. Digitry and Watlow do, among others. The SCR decides to be on or off 120 times a second. This makes the power look and act proportional, which is much easier on the elements, and gives more precise temperature control. They can also be adjusted to lower the high end of power use, if you happen to be too close to throwing breakers or stressing your wiring system.

Al, if my memory serves me correctly, Watlow does not charge for the software you need to interface this controller with a computer. If I am right, this is a significant factor. I know that Digitry does charge for theirs.

[Babette (Shawn)]

Thank you Bert and Al, I am now on a mission to learn more about controllers and relays! So far I have looked on eBay and googled Digitry & Watlow. I know I want to buy a new (as opposed to used) controller since I had a very frightening experience with a run-away kiln last year. I think I would benefit from using a controller that offers "more precise temperature control" because I tend to make larger & thicker pieces. Also, I can't help but to notice that many companies that make controllers do not make kilns..

It would be interesting to see what set ups (controllers, relays, thermocouples & shelves) other glass people on this site are using? Are most people buying "complete Packages" from Paragon or Skutt or Evenheat , etc.? How many people are putting together their own custom setups?