Bisque firing ,bungs in and out when.

[Babs]

Just asking because .

Whe  bisquing I have all bunbgs out till 700degC then put all in except one on lid, top loader electric.

Done this for years, still solid logic?

No vent

 

[Chilly]

The big kiln at the centre only has one bung.  As it fires over the weekend ( I set it up on Wednesdays - at least I did, until covid), I'm not there to play with bungs.

Same with my own little kiln, side bung is in, top bung is out.  As it goes on overnight with Economy 7 cheap rate electricity the bungs stay put.  Can't be messing.

[neilestrick]

On 11/11/2020 at 3:47 AM, Babs said:

Just asking because .

Whe  bisquing I have all bunbgs out till 700degC then put all in except one on lid, top loader electric.

Done this for years, still solid logic?

No vent

 

Still good. But you could just leave the top out and not mess with the others if you don't want to.

[Magnolia Mud Research]

If the clay body requires any combustion, logic seems to prefer having separate incoming and outgoing openings for the  gases.  At least that’s what my physics and  engineering schools recommended.

[liambesaw]

21 minutes ago, Magnolia Mud Research said:

If the clay body requires any combustion, logic seems to prefer having separate incoming and outgoing openings for the  gases.  At least that’s what my physics and  engineering schools recommended.

Since air is so thin when it's past say 1000 degrees, is there really much convection happening?  I have a feeling a kiln with a vent is 1000 times more efficient since there's no draft in an electric kiln.  Is that right? Or is the gas exchange not really that significant in an electric kiln.  I've never had carbon coring or anything in an electric kiln, regardless of peep arrangement.

[Bill Kielb]

3 hours ago, liambesaw said:

Since air is so thin when it's past say 1000 degrees

I would agree, the atmosphere is so thin at high temperature  we never feel  or observe anything push out a spy hole  when we remove a port plug. That said leaving a plug or two out seems to have very little negative effect on firing time as well. A power vent is definitely more effective and a properly operating one removes an extremely  small amount of kiln air per minute when we  actually measure it.

[neilestrick]

1 hour ago, Bill Kielb said:

That said leaving a plug or two out seems to have very little negative effect on firing time as well.

In a bisque it won't really matter. But in going to cone 6, leaving too many peeps out will affect the firing time, or even prevent the kiln from reaching temp. About once a year I get called to fix a kiln that ins't broken, they're just leaving all the peeps open because they broke all the plugs.

[Bill Kielb]

 

1 hour ago, neilestrick said:

leaving too many peeps out will affect the firing time,

I believe it! 
The qualifier “That Said leaving a plug or two out seems to have very little negative effect on firing time as well.” all plugs, for the whole firing probability not good.

[Pres]

I have always had a tendency to leave top two plugs out, when bisquing. The glaze load gets the top two out until 1200F. , Then I put them in. I have had problems in the past with poor color and found that the plugs out helped get crisper brighter colors. Firing down slightly also gave me a little more depth and crystallization.  Some of this may have been because of waxing bottoms.

 

best,

Pres

[Bill Kielb]

1 hour ago, Pres said:

have always had a tendency to leave top two plugs out, when bisquing

Sounds logical and likely has little effect on firing time. Not a whole bunch of air moves around after red heat but I suspect small amounts are just what the doctor ordered. Time tested! Wax is always difficult through about 800 degrees even with a downdraft vent.

[Pres]

@Bill Kielb, you may not realize that I fire without any controllers or setters. My L&L was ordered without them in the 80's. I have fired almost entirely with heat color and cone packs. However, am considering a controller to make life easier as I get older.

 

best,

Pres

[Bill Kielb]

@Pres  I actually do (read your stuff) and you are probably the last person I can think of that fires by color which is impressive . It was an extremely important skill  in early use of kilns. Humans can actually do some amazing things. Damage to eyesight was an occupational hazard. I like electronics a whole bunch but most often we struggle to emulate human skills with what seems like electronic precision. Controllers likely good for most folks though but the lessons of heat color sort of lost in textual explanations likely never to be learned with appropriate appreciation.

[Pres]

Eye sight is still good, but my tendency to fall asleep, or miss an alarm is becoming more possible. Watching a kiln constantly is tedious and exhausting. I have pretty well timed firing length to make things easier, but then replacing elements, varied packings and changes in my electric from the city are factors that make constant monitoring necessary. We all deal with it so pot on!

 

best,

Pres

[Mark C.]

On 11/13/2020 at 7:55 AM, Pres said:

@Bill Kielb, you may not realize that I fire without any controllers or setters. My L&L was ordered without them in the 80's. I have fired almost entirely with heat color and cone packs. However, am considering a controller to make life easier as I get older.

 

best,

Pres

Seat of your pants firing Pres-its what many of us old timers  do. I fire all bisque without cones in gas kilns.Color is key.

One needs to know what the real process is and not take for granted all the time modern convinces .

[LisaJJ]

Hi, new to this thread, just started making again after 15 years break. Just received my 1st kiln, Potclays Silver top loader S39, electric. Question, on a bisque fire, do I leave the bungs in or out? My manual says to leave them out on bisque but insert the top spy hole at 500 degrees. Thanx in advance, Lisa.

[Mark C.]

leave out top spy plug until all water vapor is gone-500 degrees sounds fine.

Welcome to the board

Edited July 31, 2021 by Mark C.

[Chilly]

I never put them in.  On both top loader and front loader.  

[Paula K]

Hello - I'm a complete newbie and have just bought my first kiln an electric Rohde 43 top-loader. It has a vent at the bottom and an exhaust air socket at the top right. There are no peepholes and it uses a Stafford controller. The instructions say to leave the bottom vent open until the kiln reaches 600 degrees then close it, and the shop told me to put a bung into the air exhaust opening also at 600 degrees when bisque firing. Apparently this is to increase the kiln efficiency to reach the higher temperatures. Does this sound right? What about when doing glaze firings?  Should I also use the bung in the exhaust when glaze firing? I've never fired a kiln myself before - my work previously was fired at the school I attended. Thanks in advance

 

[Bill Kielb]

Hmm, yeah, this would confuse anyone. The truth be told in a bisque firing it’s really good to ventilate your kiln to help remove or oxidize the organics being burned out. The problem is how much? As the more you ventilate, the more energy it takes to heat. Sort of like leaving a window open in your house and heating it. Anyway the truth is a very small amount of ventilation is a great compromise.

For bisque, at some point, all the organics are gone so there is no need. In glaze firings a little bit of oxidation brightens up the glaze colors for similar reasons.

Your kiln manual provides the most consistent advice and some ventilation (a tiny amount)  will also improve the life of your elements by removing harsh corrosive gasses, especially during the bisque. After 600c though most everything is burned out so closing the bottom vent is appropriate for sure.

closing the top vent will likely save energy as well as kilns are really not super air tight so there will always be some infiltration. That kiln should be piped to exhaust the fumes outdoors. The height of that pipe will affect the draw as well. The bottom port of that exhaust allows air in the room to move up the pipe and a very small amount of kiln air to be mixed in and the room air helps keep the exhaust pipe relatively cool, say 100-200c degrees

I personally would make sure it’s piped outside so folks would not breath in the fumes and not plug the bottom port of the vent after 600c just to ensure there was some ventilation. My experience - the kiln manufacture seems to have the most reasonable approach.

Edited August 11, 2022 by Bill Kielb

[Paula K]

19 hours ago, Bill Kielb said:

Hmm, yeah, this would confuse anyone. The truth be told in a bisque firing it’s really good to ventilate your kiln to help remove or oxidize the organics being burned out. The problem is how much? As the more you ventilate, the more energy it takes to heat. Sort of like leaving a window open in your house and heating it. Anyway the truth is a very small amount of ventilation is a great compromise.

For bisque, at some point, all the organics are gone so there is no need. In glaze firings a little bit of oxidation brightens up the glaze colors for similar reasons.

Your kiln manual provides the most consistent advice and some ventilation (a tiny amount)  will also improve the life of your elements by removing harsh corrosive gasses, especially during the bisque. After 600c though most everything is burned out so closing the bottom vent is appropriate for sure.

closing the top vent will likely save energy as well as kilns are really not super air tight so there will always be some infiltration. That kiln should be piped to exhaust the fumes outdoors. The height of that pipe will affect the draw as well. The bottom port of that exhaust allows air in the room to move up the pipe and a very small amount of kiln air to be mixed in and the room air helps keep the exhaust pipe relatively cool, say 100-200c degrees

I personally would make sure it’s piped outside so folks would not breath in the fumes and not plug the bottom port of the vent after 600c just to ensure there was some ventilation. My experience - the kiln manufacture seems to have the most reasonable approach.

Thank you