# Casting aluminum.



## steamengineboy (Jan 20, 2017)

I want to cut up some old small engine blocks to melt down and cast steam engines. What is the best way to get the paint off of the block?


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## Terrywerm (Jan 20, 2017)

I don't think that you need to worry about the paint. It will burn off during the melting process and any resulting residue will simply float to the top as dross which you skim off before you pour anyway.

On the other hand, if you are certain that you want to remove the paint prior to adding pieces to your melt, sandblasting would work, or you can dip the parts in Zip Strip or other paint and varnish remover. You will probably have to coax some of the stubborn paint off of the metal with a brush, but it should come off easily at least.


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## jocat54 (Jan 20, 2017)

Terry is right it will burn off and then you can just skim it off the melt


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## gi_984 (Jan 20, 2017)

Physically remove/clean as much paint, grease, etc off any metal you want to smelt.  "Burning off" contaminants in the furnace while smelting doesn't work.  Most contaminants go into solution  and are almost impossible to get out.  Even after repeated fluxing.  The cleaner the scrap is you put into your furnace the better the quality of your alloy will be.  Much fewer inclusions and problems with your castings.  And yes I smelt lead and aluminum for projects.  I currently have two different furnace set ups.  One electric furnace for lead only.   The other is made of fire bricks and uses a propane burner to smelt aluminum.  Hoping to set up a waste oil furnace "  http://www.artfulbodgermetalcasting.com/ "  to smelt cast iron for some future projects.  His book is very good by the way.
Two things:
1.  Purchase Lyle's video set (MrPete222)on foundry work .  Excellent video tutorial on basic smelting and casting.  He taught foundry work in the high school.

2.  Get both of these books.  Really paperback shop manuals.  I got mine thru the interlibrary loan system.  Detailed how to shop manual for teaching foundry work.  Easy reading and incredibly helpful.  This is the reference that Lyle talks about in his foundry series.

https://www.amazon.com/s/ref=dp_byl...field-author=Fred+T+Cowles&sort=relevancerank


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## brino (Jan 20, 2017)

Hello, @steamengineboy 

Welcome to the site!

If you haven't seen it there is also a bunch of info here:
http://backyardmetalcasting.com/index.html

This is the burner I currently use for melting aluminum (and many other things, like: heating steel for easy bending, boiling water for "steam bending" of wood, pre-heating cast items before welding/brazing, etc.):
http://backyardmetalcasting.com/oliverburner1.html

Please feel free to share any projects you have on the go.

Have fun and be safe!
-brino


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## rwm (Jan 20, 2017)

I am of the camp that paint will not interfere with your melt or the final alloy. It will burn off. I have done it many times. If you have super heavy paint on something you might debulk it a little but don't go crazy. Alloy selection is far more important and engine blocks will be good material to use. 
Do not expect your castings to machine as well as 6061 or other commercial alloys. Unless the are T6 heat treated they won't machine as nicely. You can heat treat them but that is a whole 'nuther can of worms.
Robert


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## steamengineboy (Jan 20, 2017)

I've always thought you wanted to get any paint or dirt off before melting because less dross is better. I've cast with none painted aluminum but I didn't know about this stuff. Thanks for the answers


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## rwm (Jan 20, 2017)

When I said it will "burn off"...some will; some will end up in the dross. You will skim off the dross before you pour so you have a shiny metal surface on top of your melt. If you were using something like cans, you may have more dross than metal so that becomes a problem. A little dross is expected and OK.
Robert


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## steamengineboy (Jan 20, 2017)

rwm said:


> When I said it will "burn off"...some will; some will end up in the dross. You will skim off the dross before you pour so you have a shiny metal surface on top of your melt. If you were using something like cans, you may have more dross than metal so that becomes a problem. A little dross is expected and OK.
> Robert



Yes I've cast before but its always been clean metal. Not much dross. I just didn't know if all they paint would contaminate it too much


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## DaveInMi (Jan 20, 2017)

I try to get things only as close to perfect as necessary.  I have melted small engines with paint and oil many times.  Never have I noticed any quality issues.  I pour at as low a temperature as I can and still fill the mold without cold shuts.  It machines better than some of the structural aluminum scrap that I have.


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## The artfull-codger (Jan 31, 2017)

I've never bothered to clean off paint only oil grease etc, I usually melt more than I need & make ingots with the surplus [I have been known to not melt enough on the odd occasion- oops]  I use extruded alloy for plaques etc & cast alloy for important things, folk get to know you[at my age] & I allways get stuff given, never bought any pot fodder.


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## benmychree (Oct 3, 2017)

One thing that I learned from using permanent mold castings (pistons, small engine blocks) is that, due to added iron in the aluminum alloy used, the solidification range is narrowed, necessitating raising the melt to higher temperatures to avoid having areas of the casting solidify before the casting is complete; if you raise the temp high enough to avoid this, excessive shrinkage or cracking may be the result.  The best scrap to avoid this is aluminum that has been previously been cast, as indicated by the sand cast finish.  Structural aluminum scrap has the same problem as die cast aluminum.


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