Grog

[MRA]

Hi Folks

I'm assembling bits and bobs to build my furnace - for the first attempt I'm going to use a lining of fireclay plus...grog.

From what I've read it seems the 'bits' in my refractory concrete will be there to lessen shrinking and cracking of the clay-plus silica-sand mortar - that's what the potters seem to say.

Some use Perlite, and some use broken up firebricks. Some say Perlite melts at too low a temp. I'm having trouble finding the latter where I am, and although I'm still searching for a broken clay fireback, I've not yet found one. I did read that Belfast sinks (is that a UK term?) are made of fireclay, and I have one of those I could smash up...any comments? And if that works...old toilets? Crockery??

cheers
Mark

 

[Cogsy]

Grog??? In Aussie speak you're going to mix beer into your fireclay...

 

[skyline1]

Trust the Aussies to come up with that one.

I believe its an English Naval term actually when applied to drink hence "feeling groggy" *beer*

But it is also the term for finely broken firebrick. A good source of firebricks is old night storage heaters some of them contain the white unglazed firebricks that are ideal for making furnaces I built both of mine out of old storage heater bricks.

I don't know what your location is Mark but if you are in the U.K. I can put you in touch with a company that specialise in this sort of thing

Regards Another Mark

 

[rcfreak177]

Yep, Plenty of grog was consumed in order to make my furnace.

I used a product made by Sila, This is a pre mix type refractory cement. Al you do is add water and mix, It did appear to have crushed fire bricks in the dry mix, Apparently also Portland cement. I would advise using the premix stuff.

Baz Thm:

 

[MRA]

Thanks Folks

Another Mark - I'm in Manchester. I've used a supplier in Liverpool for fireclay, and I'm attempting to be resourceful (cheap) before spending money on anything else!

 

[chipenter]

Cheapest is cat litter Fullers earth Bentonite the whiter the better , Perlite from B&Q , its a bit soft good enough for bronze though .

 

[Herbiev]

Once you've mixed in your slab of Emu larger you can melt down the cans

 

[kye]

in terms of using both perlite and grog for the refractory, a better approach would be to use a mix with a high proportion of perlite since its very insulative but cant handle high temps as an insulation layer. then have another layer protecting the perlite layer, which would be in direct contact with all the flames and hot stuff that contains no perlite but lots of grog as this can handle the very high temperatures. it means more work in construction, but your going to be taking adventage of each materials better attributes which will hopefully make for a much more successful furnace in the process in terms of both efficiency and working life.

kye

 

[skyline1]

Hi Mark

Try Purimachos ltd in Bristol that's where I got my furnace materials (Well the stuff that didn't come out of old storage heaters).

Their prices are fairly reasonable and they are quite happy to supply smaller quantities. Also their tech support is super, they even made a special formulation for me free of charge for one job (9" Cold blast cupola).

Regards Mark

 

[02sheslop]

Folk on this forum claim that pearlite and similar substrates can flux the surrounding refractory, lowering its melting temperature. There's alot of information on that forum about refractories but I'm still not sure on how valid it all is as there's also alot of conflicting stuff, as well as a few extremely grumpy posters that really bring the tone down.

One thing I do like the look of though is the idea of using sawdust or ground up expanded polystyrene to bulk out the castable refractory or clay, where the stuff burns out and leaves an insulating porous texture. The head honcho on that forum seems to be a fan of doing it that way.

Sorry to use so many weasel words in this post though, i'm still trying to figure this stuff out myself.

 

[MRA]

Thanks 02sheslop - that's an interesting board, and I learned quite a bit.

Another question - I have 'found' a pile of heavy yellow clay bricks, which may well have been from storage heaters. On chipping off a lump and getting it red hot on a propane torch, it glows...and seems quite stable.

I might have a go at part-slicing these up, and splitting with a bolster, to make the inner lining. Any opinions as to whether anything nasty might lie within, which might suggest it would be unwise to approach them with the angle grinder?

Thanks
Mark

 

[skyline1]

Hi Mark

If they are a creamy yellow colour then they are the same type of bricks that I used in my furnaces, Night storage heater ones usually have a groove running along them where the heater filaments lie. I managed to cut them with a bolster chisel just like normal housebricks although they are somewhat harder. AFAIK there is nothing nasty like asbestos in them so you could score them with an angle grinder (dust mask is advised though) build them up like a wall but use fire cement not ordinary portland then skim the inside with your fireclay/grog mix. if you wish give the inside a coat of refractory glaze wash. Purimachos sell it and it's fairly cheap. Allow it to all dry and set for about a week to allow any trapped moisture to evaporate. On first firing bring the heat up very slowly over about 4 hours this will stop anything cracking and seal the glaze wash. Get it up to as hot as you can and let it soak for half an hour. then let it cool If you've got it right the inside should ring like a china cup if you tap it.

What are you going to melt BTW as these bricks are fine on their own for Aluminium or Bronze but they do tend to Erode if you are doing Cast Iron

Regards Mark

 

[MRA]

Hi Mark

Aye, they're the ones. I managed to split one along the element slot - but failed to cleanly split it again (since I need to line a 13kg butane cylinder I've prepared. It's got to be small and portable - back yard is tiny and wife is getting hissy about 'stuff' in it). I think I'll buy a couple of decent diamond wheels for my small grinder, score bricks more deeply, and make a bolster which runs the full length of the brick - last time I just ended up making grog when the split ran off.

I'm going to start with Al, and then try bronze - I bought someone's casting hobby (minus furnace) rather cheaply, and have a lot of lbs of Al, Cu and even some Sn scrap to play with. Having injured myself last year on a circ saw I'm rather more cautious than I used to be and if I try iron, I want to know what I'm doing first.

(edit to add - recipes investigated seem to look like 1/3 sand, 1/3 fireclay, 1/3 grog - but the Al scrap I bought had been standing in the rain for years and as a result I have half a bucket of what I imagine is Aluminium Oxide powder which I wonder about including!)

Thanks for advice on drying and then warming up - some way off, but just the kind of thing I might rush and make a pig's ear of...

Mark

 

[skyline1]

Hi Mark

A standard stone cutting disk in an angle grinder should score them nicely and you are right to be cautious especially with angle grinders there was a thread about it on here a couple of weeks ago.

spot on with the fireclay mix 1/3 sharp sand 1/3 fireclay,1/3 fine grog (about 1/4" down) well that's what I used.

Regards Mark