Jump to content


Photo
- - - - -

How Much Of A Gap Between A Piece And Shelf Needed?


  • Please log in to reply
32 replies to this topic

#21 Pugaboo

Pugaboo

    Lifetime artist 2nd year potter

  • Members
  • PipPipPip
  • 401 posts
  • LocationHelen, GA

Posted 22 July 2013 - 10:33 PM

Oldlady - "don't be afraid, newbies, it will some day become as familiar as your toaster."

Lol I just realized my toaster has a Cancel button last week so rather than yanking the lever up on the side to get toast out as its just about to burn I now push the little blue button that's says cancel. I have owned this toaster for a year and a half; lets hope it takes less time to figure out the basics of my kiln!

It only took me 4 times this time around to fit everything in to the kiln for my 2nd bisque load. My husband is now thoroughly convinced I am crazy... Well crazier than he thought... Since I leaped out of bed around midnight last night to race down and reload the kiln to get a better balance. That tall vase gave me fits and I have come to the realization that my plan of 2,4,6,8,10 and 12 inch high posts was a WRONG buying plan. What I really need are a bucket load of 5 inch posts and a dozen 1 inch posts for when all else fails and I am trying to get a shelf to spiral around the ones below it and none of my posts are the right length. I did figure out that by laying them on their sides and standing another post on top it all works out fine hence my dash out of bed at midnight to go mumble to myself in the garage as I unloaded and reloaded the kiln for the fourth time. I don't think the pots minded my pajamas at least they kept quiet about my bizarre attire until I left the room after all as oldlady said nobody REALLY knows what goes on in there once we shut the lid and leave the room.

The load fired through to completion and is now cooling off I'll be able to open it tomorrow afternoon and see what's what. Then gee guess what we get to do my first GLAZE FIRING! Ooo what fun... No you are NOT allowed to sign out and avoid the forum for a few days just to avoid my annoying newbie questions! I'll be good and try and keep them to a minimum... Remember now I said TRY LOL.

good night all and happy firing!

Terry
The world is but a canvas to the imagination - Henry David Thoreau

#22 Mark C.

Mark C.

    Advanced Member

  • Members
  • PipPipPip
  • 2,928 posts
  • LocationNear Arcata Ca-redwood rain forest

Posted 23 July 2013 - 01:37 AM

Terry

You can bisque pots on thier sides as well with no issues. Pile them up or stack them high.They are tougher than you may think.

Mark


Mark Cortright
www.liscomhillpottery.com

#23 Mart

Mart

    Advanced Member

  • Members
  • PipPipPip
  • 283 posts

Posted 23 July 2013 - 10:17 AM

 How does heat-work tally up? If you fire and empty kiln to a temperature (or cone), and fire it again to the same endpoint full of wares, how much percentage wise more power is used? I think I'm having calibration issues with my sitter or I'd test instead of ask, but it seems to me, over my three firings so far, that the one full load took 400% longer to fire. I'm really unsure about the sitter though...

 

(Sorry if this is off-topic, but several posters mentioned filling the kiln to save energy.)

 

If I recall, it's 360 Btu/h per 1 lbs or ~800 Btu/h (0.234 kWh) per 1 Kg ... but do not take my word for it :)

Fact is, heating up 100 or 150 units of something, takes different amounts of energy... unless physics is different in your galaxy :)

Do not forget, that kiln(interior) needs to be heated up too. If your load is only a fraction of kilns weight (includes shelves, bricks, posts etc) then it will not really matter much at all.

I have a small kiln so I can actually notice the difference. Question is, what is the optimal kiln size litres / load in litres (<max weight) ratio.

I try to keep about 1/4" or 3/8 gaps. Biggest waste of space comes form narrow 15 cm piece surrounded by 10 cm items on the same shelf and having the next shelve staring at 16 cm.



#24 neilestrick

neilestrick

    Neil Estrick

  • Members
  • PipPipPip
  • 2,728 posts
  • LocationGrayslake, IL

Posted 23 July 2013 - 11:33 AM

A digital kiln will fire in about the same amount of time whether it's full or empty, because the controller is keeping it on a specific ramping schedule. It will use more power to keep it on schedule with a fuller load, but the overall time will be about the same. On a sitter kiln the firing time can change dramatically depending on how full the kiln is. But to save energy, money and labor, you should try to fit as much as possible into a load no matter which type of kiln you have.

 

Gas kiln can be packed very tight with no problems, assuming it's designed properly.

 

Wood burning kilns are an entirely different beast. Too tight and you can choke off the air flow. Plus you need space for the flames and ash to move around.


Neil Estrick
Kiln Repair Tech
L&L Distributor
Owner, Neil Estrick Gallery, LLC
www.neilestrickgallery.com

neil@neilestrickgallery.com

#25 soilandpolish

soilandpolish

    Member

  • Members
  • PipPip
  • 13 posts

Posted 26 July 2013 - 06:50 PM

My point was just concerning the energy efficiency. Since you wouldn't fill a kiln with furniture if it had only a small load of wares, and nothing else in there absorbs much heat, your energy efficiency is not greatly affected by the density of fill. Possibly, it may even work the other way, that a large load would be less efficient because of the furniture, and because of the insulating effect delaying the radiant heat propagation.

 

But I'm a rank amateur, probably I'm just not getting something...

 

As for production potting, sure you probably want to turn out as many pots as possible, and the energy question is only one part of the picture.



#26 Bob Coyle

Bob Coyle

    GEEZER

  • Members
  • PipPipPip
  • 385 posts
  • LocationSanta Fe

Posted 26 July 2013 - 08:07 PM

The amount of total energy you use is related to heat loss and thermal mass. If you figure that the heat losses through the walls of your kiln are about the same for a given ramp, then the total thermal mass will determine the energy expended.

 

Kiln hardware has a lot of thermal mass. So if you are firing a few thin walled vessels per shelf, then much of the energy will be going to heating up the kiln walls and furniture. Since the clay vessels and the kiln shelves probably have about the same heat capacity, you could probably figure out the ratio by just weighing all the fired pieces and then the kiln furniture. But why bother... your stuck with the furniture you already have. They make some strong thin shelves that you could use but they are pretty expensive and I am not sure where the break even point would be if you bought them.

 

So in terms of thermal efficiency it is probably better to load up an electric kiln as tight as you can get it and to stack your ware for the bisk firing,



#27 Mart

Mart

    Advanced Member

  • Members
  • PipPipPip
  • 283 posts

Posted 03 December 2013 - 02:16 PM

... So in terms of thermal efficiency it is probably better to load up an electric kiln as tight as you can get it and to stack your ware for the bisk firing,


My original "why" was asked because I believe it's not really good idea to stuff the kiln as tight as you can.

Looks like I am not alone. John has repeated this in multiple forum threads. Here is one: http://community.cer...aze/#entry46867

#28 neilestrick

neilestrick

    Neil Estrick

  • Members
  • PipPipPip
  • 2,728 posts
  • LocationGrayslake, IL

Posted 03 December 2013 - 04:26 PM

I leave 1/8 inch between my pots, 1/4 inch between the pots and the shelf above. I've done it that way for 20+ years, and never had a problem.


Neil Estrick
Kiln Repair Tech
L&L Distributor
Owner, Neil Estrick Gallery, LLC
www.neilestrickgallery.com

neil@neilestrickgallery.com

#29 Rebekah Krieger

Rebekah Krieger

    Advanced Member

  • Members
  • PipPipPip
  • 553 posts
  • LocationWisconsin

Posted 03 December 2013 - 09:01 PM

For glaze firings I leave about 1  thick piece of cardboard space between each piece. My kiln is so tiny that I can only fire 8-12 small pieces.  I pray to mark's picture ;)  

Now that Neil gave me the connection and I have a  bigger kiln, I am a bit nervous thinking about how it's going to stack up.  Many of the shelves that came with it have glaze on them.  Are they safe for bisque firing 04 since the glaze will not melt? Or do i need to start grinding those shelves? 


Learning On my Kick wheel with my vintage Paragon (from the late 1960's)

#30 neilestrick

neilestrick

    Neil Estrick

  • Members
  • PipPipPip
  • 2,728 posts
  • LocationGrayslake, IL

Posted 04 December 2013 - 10:35 AM

For glaze firings I leave about 1  thick piece of cardboard space between each piece. My kiln is so tiny that I can only fire 8-12 small pieces.  I pray to mark's picture ;)

Now that Neil gave me the connection and I have a  bigger kiln, I am a bit nervous thinking about how it's going to stack up.  Many of the shelves that came with it have glaze on them.  Are they safe for bisque firing 04 since the glaze will not melt? Or do i need to start grinding those shelves? 

 

The glaze on the shelves may be low fire glaze, in which case it will re-melt during a bisque firing. Time to start grinding and washing.


Neil Estrick
Kiln Repair Tech
L&L Distributor
Owner, Neil Estrick Gallery, LLC
www.neilestrickgallery.com

neil@neilestrickgallery.com

#31 timbo_heff

timbo_heff

    Advanced Member

  • Members
  • PipPipPip
  • 177 posts
  • LocationMA / NY

Posted 06 December 2013 - 12:46 PM

One quick thought on this:

Even though you CAN stack your bique fire packed to max, it is not always a good idea:

Problems that rear their head during glaze fire such as pinholes and bloats, are  caused during the bisque fire.

One of the thing that makes these problems is insufficient oxegen presintering in the bisque fire.

When the bisque load is looser the air circulation and oxygenation are improved and thus burn out of organics is more betterer. (;

 

Not all clays need this but the ones that do, do. Usually it is the darker cone 6 and cone 10 clays that have more stuff to burn out.

All clays would be happy with more air, there is certainly no detriment except what you are doing in 2 loads, you may want to do in 3 loads.

Given that it is usually $15 or less to electric fire 7 feet of bisque, it is a small price to pay to prevent problems and have happier pots and not having to throw out pots with bloats and other issues.



#32 TJR

TJR

    Advanced Member

  • Members
  • PipPipPip
  • 1,238 posts
  • LocationCanada

Posted 07 December 2013 - 11:47 AM

This is what works for me as far as  glaze loads-I have mainly two size (nerds) shelve spacers which add a little to the stilt height . Mine are 5/8 and 3/4 inch small pieces of silicon carbide or mullite shevles. I have a few 1/4 ones but they die quickly due to fuzing no matter how much I coat them.

This glaze fire was just loaded a few minutes ago-my Third since the fourth of July -my 16th this year in my  35cub.car kiln. I have also done 12 small kilns this year in a 12 cubic updraft (firing now) and this loading is what works for me the past eons

This particular load is a bit odd as some of the forms are not my usual and take more wasted space (cannisters and a large 18 inch bowl)

This load has 36 12x24 inch advancers and is going to be fired in am to cone 11- 1/2 way down gas reduction fire in AM.

I place the pots so they almost touch and have forever with no sticking to one another. Refires will expand more and need more space as you can see they are a few in this load. As far as top space as close as I can get a shelve to clear with my nerds is what works for me all these years.

For those of us who make a living at this more in each kiln load is a key point. This may not work for everyone but it does for me which is what counts. My glazes do not expand more than almost touching the next item/shelve.

Every few years I will stick a pot to another-usually because I have shoved them together after loading them by moving them after placing them the 1st time around around. When you load a kiln like this many times all this is second nature-how tall of a stilt is needed what is the hieght of wares etc.This kiln loads in about 1 to two hours depending on how much small stuff is in it-I'm not a numbers guy counting pots but there is over 400 pieces in this load I'm sure.

Mark

Mark;

I think I see a spot in the first picture, third shelf down where you could sneak a spoon rest bestween those two big bowls. Just kidding ya. Amazing stacking.

TJR.



#33 Rebekah Krieger

Rebekah Krieger

    Advanced Member

  • Members
  • PipPipPip
  • 553 posts
  • LocationWisconsin

Posted 09 December 2013 - 06:20 PM

 

For glaze firings I leave about 1  thick piece of cardboard space between each piece. My kiln is so tiny that I can only fire 8-12 small pieces.  I pray to mark's picture ;)

Now that Neil gave me the connection and I have a  bigger kiln, I am a bit nervous thinking about how it's going to stack up.  Many of the shelves that came with it have glaze on them.  Are they safe for bisque firing 04 since the glaze will not melt? Or do i need to start grinding those shelves? 

 

The glaze on the shelves may be low fire glaze, in which case it will re-melt during a bisque firing. Time to start grinding and washing.

 

 

 

 

For glaze firings I leave about 1  thick piece of cardboard space between each piece. My kiln is so tiny that I can only fire 8-12 small pieces.  I pray to mark's picture ;)

Now that Neil gave me the connection and I have a  bigger kiln, I am a bit nervous thinking about how it's going to stack up.  Many of the shelves that came with it have glaze on them.  Are they safe for bisque firing 04 since the glaze will not melt? Or do i need to start grinding those shelves? 

 

The glaze on the shelves may be low fire glaze, in which case it will re-melt during a bisque firing. Time to start grinding and washing.

 

Blah-  but good advice. You never know so It's not worth it.  I got the grinding brick thing with the kiln.  


Learning On my Kick wheel with my vintage Paragon (from the late 1960's)




0 user(s) are reading this topic

0 members, 0 guests, 0 anonymous users