Orton vent master, lid holes question

[brettwulc]

Hi all, 

So I'm a bit new to the downdraft vent game and have a question.  I was advised to drill two 1/4" holes in bottom, and lid. It probably wasn't needed to drill into the lid because i have an older skutt and i know it's not vacuum tight. But I have it all hooked up proper and it draws a flame through each hole in the lid (when kiln is off). 

My question is (and this may be obvious) but as the kiln is on and reaching around 1000 f, heat is obviously rising and my little lid holes seem to be blowing out heat as opposed to sucking in? Is this completely normal? Can I assume my vent is still sucking in room air through those lid holes and mixing? Or am I just blowing out heat and fumes? 

Thanks!

[neilestrick]

As the kiln heats up, the interior of the lid expands more than the exterior, and you end up with a concave shape to the lid, like a contact lens. This causes it to gap at the edges. It could be that the vent is pulling there more than at the holes in the lid. As long as you're not smelling fumes, it's likely working just fine.

[brettwulc]

2 minutes ago, neilestrick said:

As the kiln heats up, the interior of the lid expands more than the exterior, and you end up with a concave shape to the lid, like a contact lens. This causes it to gap at the edges. It could be that the vent is pulling there more than at the holes in the lid. As long as you're not smelling fumes, it's likely working just fine.

Thanks for the quick reply Neil. That makes a lot of sense, I was weary to drill lid holes to begin with because I didn't think they'd be necessary.  

Would it be smart to fill the holes for the next firing? I'm not getting any fume smell, but still a little worried. 

[brettwulc]

2 hours ago, neilestrick said:

As the kiln heats up, the interior of the lid expands more than the exterior, and you end up with a concave shape to the lid, like a contact lens. This causes it to gap at the edges. It could be that the vent is pulling there more than at the holes in the lid. As long as you're not smelling fumes, it's likely working just fine.

Hmmm, on second thought I can definitely smell some fumes. 

[Hulk]

Hi Brett

I wouldn't expect kiln vent to eliminate all fumes - most, or a lot would be good.

I have a kiln vent, added an overhead heat/fume hood with a fan so I'd feel comfortable being in the studio whilst firing. 

[Bill Kielb]

1 hour ago, brettwulc said:

Hmmm, on second thought I can definitely smell some fumes. 

@Hulk is right. Downdrafts do a great job, especially ensuring your wares are oxidized  but in practice rarely can  remove 100% of the fumes.

[neilestrick]

@brettwulc What model kiln do you have?

[brettwulc]

10 hours ago, neilestrick said:

@brettwulc What model kiln do you have?

@neilestrick I have an old skutt, 231x. Still works really well, replaced almost everything I could. But when it reaches glowing red you can definitely notice the small gaps between the rings etc. 

[neilestrick]

I'd leave the holes. Gaps are normal, and it's possible that enough gaps could be spoiling the draft a bit as it gets hotter and allowing fumes to escape. You could try blocking one or part of one of the room air intake holes on the collection cup to increase the draw from the kiln.

[brettwulc]

11 hours ago, neilestrick said:

I'd leave the holes. Gaps are normal, and it's possible that enough gaps could be spoiling the draft a bit as it gets hotter and allowing fumes to escape. You could try blocking one or part of one of the room air intake holes on the collection cup to increase the draw from the kiln.

That sounds like a good idea, i’ll give it a go next round. Thanks for the info and responses from everyone! Very much appreciated. 

I’m constantly playing with switches, staggering, and density of pots to get my firings as even as possible, and wow the vent made a noticeable difference. Here are some cones from the bottom middle and top. 

[Bill Kielb]

3 hours ago, brettwulc said:

 a noticeable difference. Here are some cones from the bottom middle and top. 

Nice and even but a tad  over fired. Included firing chart below for your reference, once past four o’clock they are basically at cone. Once they over fire and begin to lay down it is hard to tell how much over fired.. To tell more accurately it’s common to include a guard cone or one cone higher

 

[brettwulc]

10 hours ago, Bill Kielb said:

Nice and even but a tad  over fired. Included firing chart below for your reference, once past four o’clock they are basically at cone. Once they over fire and begin to lay down it is hard to tell how much over fired.. To tell more accurately it’s common to include a guard cone or one cone higher

 

Thanks for the chart Bill! I forgot to mention I was firing to 05 and the only witness cones i had around were 06.