# Small furnace



## Romix (Dec 1, 2014)

Hi forum. 
I planing to build a small furnace, 100 - 200 gram melt. 
I have 2 empty Condensed milk cans. They are made out of quality steel. I checked, handles high temperatures. 

Would this light be ok for the furnace? http://www.ebay.co.uk/itm/251640800036?_trksid=p2055119.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT
What heat insulation material should I use?
Where to get quality small graphite crucibles with handles and gloves?


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## Romix (Dec 1, 2014)

Is hole on the top of the furnace important? Heat escapes through it.
Can furnace explode with out it?


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## FrugalRefiner (Dec 1, 2014)

I doubt the cigarette lighter will serve your purpose.

The hole on the top is required to allow the burned gases out.

Dave


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## GotTheBug (Dec 1, 2014)

If you want to build a small furnace, why use cans at all? A few firebrick could be positioned to do exactly what you want to do, without the risk of a burn through that you'll have using thin metal cans, and you won't have to buy additional insulation or refractory lining. And yes, a hole is necessary.


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## Romix (Dec 2, 2014)

GotTheBug said:


> If you want to build a small furnace, why use cans at all? A few firebrick could be positioned to do exactly what you want to do, without the risk of a burn through that you'll have using thin metal cans, and you won't have to buy additional insulation or refractory lining. And yes, a hole is necessary.


Do you know what material fire brick made of? 

I also wont to build a massive (Alum melting) furnace, with a lid, and a hole with a steel conduit welded to it. And dip the end of the pipe in water. 
So all the toxic fumes get filtered. Adding NaOH will stop green house gases escaping out in to the atmosphere.

Would it work by blowing air with hair dryer on burning coals. 
One thing I scared of is hairdryer melting, any ideas how I can isolate it?


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## rickbb (Dec 2, 2014)

Check out this guy's videos, he shows how to make a small furnace or a large one.

https://www.youtube.com/watch?v=uIRTcmR6sSk

He also shows how to make your own refractory cement for insulation.

Most fire bricks you get at the local supplier are not the insulating kind and will absorb most of your heat. You will have to line a furnace using that kind of brick with rock wool to keep the heat in.


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## GotTheBug (Dec 2, 2014)

Romix said:


> GotTheBug said:
> 
> 
> > If you want to build a small furnace, why use cans at all? A few firebrick could be positioned to do exactly what you want to do, without the risk of a burn through that you'll have using thin metal cans, and you won't have to buy additional insulation or refractory lining. And yes, a hole is necessary.
> ...



Not sure on the exact mixture for firebrick, though I have seen a few furnaces made with commercially available bricks with no problems at all. 
When you say "massive", how much aluminum do you want to melt at one time? I made a pretty cool furnace out of an old turkey smoker that works dangerously well, and will melt a 20 or so pound pot of aluminum easily. Aluminum is extremely easy to melt and use, for casting etc. I typically bring it to 1500 F so it retains heat long enough to be poured where I want it. 
I've not given much thought to running the fumes through a scrubber, as my aluminum process allows the pot to sit on top of the furnace with the lid off. I do wonder if the added resistance of pushing the very hot air through a scrubber will cause some outgassing where the lid sits on top of the furnace.

A hair dryer will work for a small amount of aluminum, but might not deliver enough air flow for larger batches. My air supply in the "small" foundry is a leaf blower with a dimmer switch as a rheostat to regulate airflow. At full volume, it would probably launch sparks up to low flying aircraft. 

Isolating your air supply is easy, just use a longer feed pipe. Mine is just under 3 feet from blower to where it enters the furnace, and have not had an issue. Just make sure you leave the air supply on after you are finished and until the furnace has cooled down, as the hot air will absolutely feed back up the pipe and into your blower if you shut it down too early.

I think the site is backyardmetalcasting.com, lots of designs, tips, etc. to be found there.

Paul.


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## Romix (Dec 5, 2014)

I seen lots of videos on youtube, where people melt alum.
Most of the furnaces had rounded lid, that just wrong!! What a waste of heat! 
Lid have to be straight, so you place your beakers on it, to speed the reaction up.


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## Romix (Dec 24, 2014)

GotTheBug said:


> Romix said:
> 
> 
> > GotTheBug said:
> ...



Thank you for advise. 
How far away from the bottom airblowing hole located?


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## NobleMetalWorks (Dec 24, 2014)

You do realize that a simple small jewelers torch would be far more efficient than a tiny little furnace. A furnace that is too small, defeats the purpose of using a furnace at all. What essentially you are doing, is creating a less efficient use for a small torch. If you use a jewelers torch, a very simple, very small one, you will not only NOT use very much gas/oxy, but you will melt your metals far faster, which leads to less loss.

Scott


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