stainless steel needles V melt fibres in homebrew

[Poochdog12]

and one know about these products, and which is best to use in a homebrew mix for a mobile pizza oven

[Poochdog12]

sorry was meant to say.. which is best,, ss needles or polypropylene

[UtahBeehiver]

David S has describe the use of melt extract needles as well as polypro fibers and if I call right, they each have a different purpose in the casting process. So do a search under David S and melt extract needles.

[Poochdog12]

cheers mate. will do

[david s]

The stainless needles (melt extract fibres) are the recommended reinforcement for refractory material. The fine polypropylene fibres (finer than human hair) as used in concrete reinforcement to improve compressive strength, can be used as burnout fibres. They do not in this case enhance strength, because they melt at 160C, leaving a network of tiny pipes through which water vapour can find its way out. They do not reduce the density of the refractory, but do provide a measure of protection from steam spalling when the material is first fired when it contains a lot of moisture.Proprietary cartable refractories have them added in the mix already, a home-brew mix does not and they should be added.The addition of the needles is optional IMO because they are both expensive and hard to work with (they are not called needles for nothing).

[aaronpizza]

DavidS you're right the SS needles are hard to get hold of AND rather expensive!

If they are left out, would you add something else in place/increase the cement part? or anything else ?

I'm currently considering leaving them out...

[Poochdog12]

Thankyou,,, I did wonder how tricky it would be to work with a concrete that you want smooth, that has needles in. Thankyou for your insight. ill check prices and see. What length are they?

Arron if the the needles are to expensive and and hard to get hold of. You’d be best using the burnout fibres? Sounds like the companies put them in there products, so you’d be best to put some in yours to be be fair. There was a ratio posted on here somewhere..... I think it was for the Ss needles mind.. 3% weight of dry mix. Not sure if that’s the same for propylene.

[david s]

DavidS you're right the SS needles are hard to get hold of AND rather expensive!

If they are left out, would you add something else in place/increase the cement part? or anything else ?

I'm currently considering leaving them out...

The homebrew makes a pretty good castable for the temperature range of a wood fired oven. If you want a slightly better castable then go for a proprietary dense castable refractory. For the small improvement you will pay a lot extra. One advantage is that it should already contain the burnout fibres so you wouldn’t have to access them.
Don’t stuff around with the homebrew recipe, it’s tried and tested and works pretty well. Also don’t be tempted to use rebar reinforcement, it is not compatible because of its high conductivity combined with high temperature ramp.

[Poochdog12]

i suppose if saving money on the homebrew, then its worth spending that extra on the ss needles.

im really wanting your feedback on my dome floor configuration guys, i was thinking on my checkered plate base id put 4" vermicrete / perlcrete.
1" cast homebrew floor, ( in two sections thanks david)
firebricks ( laid loose thanks david)

whatcha reckon

[david s]

Lots of considerations: what is your planned oven size?
Have you calculated the weight?
Trailer axle rating?
Single or double axle?
How thick is your checkerplate?
What supports the checkerplate?

As s general rule the oven will be heavier than you think.
Consider shocks on the trailer springs.
A heavy oven will require a V8 to haul it.

[UtahBeehiver]

This thread has been moved from Ask Me Anything to the correct Other Oven Types

[mesoiam]

I couldn't get hold of any stainless fibres but have got some non-stainless on the way. The seller said they should be fine and have been used in castable ovens before. Stainless would be ideal but just can't get them in domestic quantities in the UK. So my question is, would non-stainless needles be better than nothing or worse than nothing for the homebrew castable? I will be adding polypropylene fibres to the mix also. Thanks in advance for any thoughts or experience.

[UtahBeehiver]

I think you need to confirm with David, my guess he will be concerned about corrosion of the melt extract fibers.

[mesoiam]

Thanks, I've now got the real deal on order and was able to cancel the non stainless ones. Stainless fibres from Rockbond.co.uk, cheers to Nick J C for the tip.