Confused about fluxing.

[Sitsinhedges]

I have a load of linotype to alloy with pure lead and am a little confused about the process of fluxing to get out impurities.

I understand that if I put a bit of candlewax in it is supposed to bring the impurities in the lead up to the top as a slag, but I also understand that tin and more importantly antimony tend to sit on the surface of the molten metal and oxidise with contact to the air.

I don't understand how to remove impurities as a slag without removing the antimony. Am I supposed to have a layer of candlewax melted on the top to keep the metal and air seperated so that oxidisation can't occur.

There seems to be two types of fluxing, one to purify and one as a cover.

Really would appreciate a clear explanation as I don't want to lose all the metals that I have gone to this trouble to include.

Thanks in advance
Andy

[dromia]

Fluxing helps get the oxidised metals back into the melt.

All you need to flux really is carbon,I stirr my melt with a dry dowel stick, the hot alloy chars it and it puts carbon through the melt.

I then scrap the sides with a spoon a pull all the dross and metal "scum" to the side of the pot.

I then press this sludge between the edge of the pot and my spoon, the metal sludge dissappears backinto the melt and when its all gone you are just left with a grey dust of burnt carbon and any impurities that have come out.

I then just skim off this powder for disposal, this way gets the oxidised alloy back into the melt.

Glenn Fryxell's article describe fluxing as good as most I've read,his articles are here:

http://www.lasc.us/ArticlesFryxell.htm

Read "The Simple Art of Fluxing"

[docone31]

I am not sure, what flux actually does. I do know, if there is no fluxing, there is no flow.
I use beeswax for fluxing my melt. It does a good job. I use a wood dowel for stirring. I like the carbon in the melt. I use borax on top of the melt when casting. It clumps up and pulls the dross. Sawdust is too smokey for my taste when I am casting.

[leftiye]

Counting covering the melt, then there are three types of fluxing. True fluxing only captures the impurities on the surface of the melt (hence - stir). What we often call fluxing is actually reducing the oxides into pure metal thus allowing them to re alloy with the melt. Reduction is usually accomplished with a carbon donor, wax, rosin, motor oil, stearic acid, wood shavings, rubber balls, cats, Ivory soap, boolit lube to name a few. Always stir with a stick, anything else is a foolish waste of effort.

[Junior1942]

I haven't fluxed in over twenty years. Thousands of bullets later, it has made zero difference.

[montana_charlie]

I understand that if I put a bit of candlewax in it is supposed to bring the impurities in the lead up to the top as a slag, but I also understand that tin and more importantly antimony tend to sit on the surface of the molten metal and oxidise with contact to the air.
You have the wrong grip on this bundle if information.

Once alloyed with lead, tin and antimony don't 'sit on the surface'.
The surface contains all of the metals that make up the alloy, each in it's specified percentage.
But, the tin will oxidize more readily than lead, so the 'grey crud' that accumulates on the surface has a gradually increasing tin component.

If you were to scrape that crud off and throw it away, the percentage of 'lost' tin would be (somewhat) higher, compared to the discarded lead and antimony, than the percentage of tin in your alloy.

Using a wax (or whatever) 'flux' when melting down a load of scrap will (supposedly) help the desired metals to spread evenly throughout the mixture as chunks of varying alloys become liquid. Stirring will help cause trapped 'undesirables' to come to the surface for removal.

Using a covering 'flux' is to prevent air from reaching the surface to retard, or eliminate, oxidation of the metals in the alloy.

Using a carbon 'flux' to clean the surface of the (actual) metal you are using for casting is to 'reduce' oxidized materials back into their original metal form so they can recombine with the alloy...preventing you from throwing away valuable metal in the form of skimmed-off 'crud'.

CM

[Sitsinhedges]

Well I mixed a few batches tonight, mixing 2 parts old lead pipe to one part linotype and stirred it with a stick. putting in a small amount of candle wax and stirring whilst the smoke burnt off ended with a dry dust accumulating on the surface which was skimmed off. What I am left with seems to be about the same as straight wheel weight lead whose hardness seems to correspond to about 5% antimony. The tin may have added to the hardness though.