Medium vs Fine grade Vermiculite?

[Tscarborough]

Re: Medium vs Fine grade Vermiculite?

Yep, but I bet they are not tearing them down like they used to. They are still knocking down a few in Chicago where most of mine come from, but not like they were 10 years ago.

[aeu99217]

Re: Medium vs Fine grade Vermiculite?

That would explain why they seem to be relatively common here in Glasgow given that many of the buildings were built during empire days. Wilson and co is printed on the bricks and i was told that they used to emport them to oz in the 30s.

[Tscarborough]

Re: Medium vs Fine grade Vermiculite?

They are rare because they are from old buildings. There are very few brick manufacturers in the US making dry pressed brick, other than for firebrick. There is one local to me, but the brick are of poor quality and are still half the price of firebrick, there is no way I would use them in an oven.

I have a bunch of handmade adobes I want to build an oven with (because I got them free), I have thrown them into bonfires with no ill effects, so they will probably work as well, but the cost is more than firebrick normally.

[dmun]

Re: Medium vs Fine grade Vermiculite?

Just a side note: If you are hiring a mason the labor costs will always dwarf the material costs, making this a pricey project. The cost of a few firebricks is a relatively minor factor, if you are springing for a professional build.

[aeu99217]

Re: Medium vs Fine grade Vermiculite?

well let's hope mine are that type. I had someone from oz have a look at photos of them and he asked me to bash them up: he seemed to think they are ok. I got them from old tenement buildings which are about 100 years old (the bricks themselves probably arent that age as they are from internal walls) so i wonder if they are rare because they are mainly found in old buildings?

Certainly if the difference is that little then obviously firebricks are the way ahead but if old pressed reds are available for much less in the local area (in my case nothing) then the risk might be worth it.

Nonetheless, only time will tell as to whether the bricks are suited. Fingers crossed

[Tscarborough]

Re: Medium vs Fine grade Vermiculite?

Dry pressed solid commons as a rule are fine. They are also not very common and cost almost as much as firebrick in most parts of the United States. For example, I sell used solid commons for .80 each and firebrick for $1.40, so for an average oven you will save maybe a 150 bucks?

And that is if you can find the right kind of bricks, because 90% of what are available are not the right kind over here. Unless you can tell, and I assume his mason can, why take the risk?

[aeu99217]

Re: Medium vs Fine grade Vermiculite?

it wont have cost me anything cause i got the bricks for free off gumtree.

They aren't any old engineering bricks though. They are old pressed reds which according to the aussies can cope with the demands of back garden pizza baking. Summers in Glasgow last for 4 weeks, if you're lucky, so it's not going to have to withstand industrial scale cooking.

[Tscarborough]

Re: Medium vs Fine grade Vermiculite?

How much did you save if you have to tear it down and start over again?

[aeu99217]

Re: Medium vs Fine grade Vermiculite?

i've built mine out of old pressed reds as i didnt want to spend hundreds on firebricks which seem to be more expensive here in the uk. However, i did ask on this forum and there seems to be a school of thought emanating mainly from oz that old pressed reds can be used as they were fired at a higher temperature. Next week i'll be ready to start firing the oven so i'll post back in a couple of weeks and let you know how i got on.

[Rolaed]

Re: Medium vs Fine grade Vermiculite?

Are your oven dome and walls all firebrick?

[leckig]

Re: Medium vs Fine grade Vermiculite?

I dropped one of those red bricks on my foot once. Horrible experience it was!

Seriously: he is right.

[Rolaed]

Re: Medium vs Fine grade Vermiculite?

Thanks for the responses. I poured the suspended cement oven base yesterday. Tomorrow I will do the vermiculite.

The mason I hired is trying to convince me not to use old red bricks as the oven walls/ceiling. I plan on firebricks for the base and to save $$$, I planned on old red brick as the walls/ceiling. The mason says it will not last one season and to go firebricks all the way. Any bad experiences with old red brick from others is appreciated.

[leckig]

Re: Medium vs Fine grade Vermiculite?

you can rent a concrete mixer from Home Depot or Ace Hardware for less than $30. Do it!

[dmun]

Re: Medium vs Fine grade Vermiculite?

Standard readymix quickrete cement will do here I suppose?

Two different things. Readymix is the stuff that comes in the big truck. Quickcrete concrete mix comes ready to add water in bags. Either will do fine: Needless to say having the readymix truck come in saves a lot of work.

If you are going to mix your own concrete, get help. It's a lot of work, and you want to work fast enough to pour the entire slab before the first batches set up. A mixer is a big help.

I didn't bend the end of my rebar. Stuff's hard to bend. No rebar in the insulation layer.

[Rolaed]

Re: Medium vs Fine grade Vermiculite?

A 4 inch suspended slab with about 1% rebar by volume is plenty strong enough (0.5 % each way). Do some research or get advice on rebar placement. Do not have "loose ends". Rebar ends should have a hook or a 8 to12 inch right angle bend.

I finally got the cement blocks mortared in place. I need to do the cement slab next. Standard readymix quickrete cement will do here I suppose?

Should the rebar grid be at 1 foot spacings? This is the first mention of hook in the rebar that I have come across. Should the hook go into the holes of the cement blocks? Not sure what is meant by loose ends??

After the cement block comes the verimculite. The formula is 5 parts vermi to 1 part portlamd cement , correct? No rebar in this step either?

Any advice from the oven masters is appreciated.