View Full Version : fluxing questions
05-15-2007, 04:47 PM
ok guy's i did some smelting today and fluxed with candles. after getting everything up to temp and the clips picked out i turned down the flame some and tossed in about a inch of candle and went to stirren with my ladle, cup side down with a up to down motion just like i learned from a book 100 years ago. anyway after i had enough of it i still have stuff that looks like aluminum pait floating on the top. the same book i refered to said that its the tin and needs to be fuxed back in and dont throw it out, so i kept fluxing! finaly i gave up. am i doing something wrong? should the melt look like chrome on top when its ready? maybe im just trying to be to criticle? should i just scoop it out? is it my tin?
this may sound like beginer stuff but im trying to do a better job of casting that i used to years back.-phil
05-15-2007, 05:09 PM
Rather than typing it up again, here is a link to an explanation of stick fluxing.
See if the 'stick' makes sense to you.
It is one way to recombine (the term is 'reduce') oxidized metal with the rest of the alloy...leaving that chromed look on top.
05-15-2007, 05:37 PM
My experience has been that if you smelt your WW and let the temperature rise to about 600*F it will become easy to remove the clips plus a bunch of black stuff. By the time the temperature reaches 650*F the melt will be shiny on top, but each minute or so it will turn grey. At that stage you can remove a rather tiny amount of oxide, or you can leave it there - I skim it just before I pour ingots, but from my bottom pour casting pot I just leave it to form an insulating layer and retard further oxidation. When pouring WW ingots I gently scrape around the inside of the pot with a stainless spoon and a bunch more black dirt comes up - previously it was stuck to the sides and bottom of the pot.
I stopped fluxing some time ago when I formed the opinion that it made no difference. However if you hold a potful of high-tin alloy in a molten condition for long enough - possibly years - you'll lose more tin than you want to. This is a major reason that printers considered linotype alloy to become exhausted or used up after it had been in linotype machines for very long periods - a potful of alloy is kept continuously liquid in those machines.
So, tin does oxidise faster than other constituents, but probably not much faster. I think the story in the Lyman manual that suggests tin is lost quickly from molten alloy is wrong, and I think this is demonstrated by the printing industry's ability to keep linotype molten for many months or perhaps years before the tin became seriously depleted.
05-15-2007, 07:09 PM
That "zinc plated" look on the surface will reappear every few minutes no matter what you do. Grumpy one is right, leave it alone, it serves as a barrier to oxygen.
05-15-2007, 07:51 PM
See thread- "Losing the tin in Dross- Truth or Myth" 7 April 07. Really covers oxidation and fluxing. There are a muy many posts on fluxing- see under search.
05-15-2007, 08:46 PM
Depending on the capacity of your pot and the diameter of the candle, "a inch of candle" may be more than you need. I use a lump of candle wax about the size of a big pea for fluxng ten or twelve lbs. of alloy. Also, by stirring with your ladle "cup side down" are you trying to mix air into the melt? I have seen such advice in old books and it's not a good idea. Oxygen causes oxides, which are not our friend. These days, I gently lower the ladle into the alloy and stir thoroughly, paying particular attention to scraping the sides and bottom of the pot. Naturally the freshly skimmed surface doesn't stay silvery very long. A ladle caster must rake the dross out of the way before every time the ladle is filled. The ladle is a good tool for this, especially the RCBS ladle with its fin on the bottom. Usually I have to flux and skim again after about 15-20 casts.
05-16-2007, 09:23 AM
yesterday, on my second pot full i fluxed with candles untill i was tired three times and i have to tell ya, i didnt see where it did anything! i guess when i was younger i could just follow directions from the lyman book, and not question it. i always thought i was doing something wrong because i didnt see the results that the book seems to indicate that you will get. today im going to try out some of your ideas begining with just useing a wood stick, and i bet it will be more effective. as far as pine needles, i got plenty, and there good and dry to. it aint rained here in so long a dirty look could cause a fire.--phil[smilie=1:
05-16-2007, 10:05 AM
Chevy, You might want to stop stirring etc for prolonged periods of time. I never have. If the flux you're using works you will get shiny metal almost immediately, plus some **** floating on top (skim it off or don't as you wish). Using a stick to stir with (I like a piece of hardwood dowel) is a very good idea. The best fluxes are comprised of the ingredients of (surprise) soldering fluxes. Rosin and beeswax together are super. Crushed charcoal, sawdust, or kitty litter for your oxygen barrier (may work better if it continues reducing the oxides?). Fwiw the "shiny metal thing only lasts momentarily before oxides begin forming again. You have to just live with it. Lower metal temperatures produce oxides more slowly. Keep your mold hot (mold heater) and your metal can cast at a lower temp.
05-16-2007, 04:44 PM
well i gave a hardwood dowel a workout today and i have to say it worked as well as anything else so far. i didnt see where it did anything! i just dont think anything puts the stuff that looks like aluminum paint floating on the surface back in the melt. the good news is i aint going to worry about it anymore! i nolonger feel im doing something wrong. im going to stirr with a stick, skim the silver stuff off and pour into ingots, and move on. i got almost half of my new stash cast into ingots and im going to take a break from it and do some bullet casting for a wile.--phil
05-16-2007, 06:41 PM
Phil, you've ended up right where I am. You need to get the garbage out, but candles, sawdust, sticks and spoons seem to do exactly the same thing as far as I can tell. The stick is probably the easiest to use, but it gets used up in the process and I have to switch to the spoon anyway to skim off the grunge. I do think sawdust pushed down into the melt cleans it faster than other methods, but I don't think it ends up any cleaner.
I do recommend that you pour from a clean surface, though. Skim just before you pour your ingots, so you won't have oxide inclusions in them, and try to minimize the grunge on the sides and bottom of the pot for the same reason. Dirty ingots make defective bullets; dirt or oxide inclusions in the melt end up in the bullet, and aren't likely to happen to be precisely on the centerline.
05-16-2007, 07:27 PM
If you have a thick (1/16 inch or more), lumpy gray scum on top of your melt that won't combine during fluxin' 'n' stirrin', it's stuff you can and should skim off and trash. If you just have thin, dull spider-webby or cracked mud looking film on top of a shiny surface, leave it alone and cast.
While fluxin' 'n' stirrin', be sure to scrape the sides of the pot once in a while and trash all the **** that floats to the top.
("Boolit Master" at last!)
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