Dross - did I do this right?

[Markbo]

When I smelted my wheel weights into ingots, I fluxed using wax. got a lot of dirt and gunk out of it or course. Now I have melted down my first ingots for casting. Melted it down and fluxed just at the start. I got what I can only describe as fluff. It reminded me of when you boil food too hot and get this fluff on the top... make sense?

Anyway, it didn't appear 'dirty' by sight, but it didn't stir back in easily so I scooped it off. Is that the right thing to do or should I put it back in on the next casting session? What I don't know is did I remove anything I need or is this just gunk to be disposed of? FWIW the pot was just at melt temp so it wasn't super hot.

Many thanks

[oneokie]

When I smelted my wheel weights into ingots, I fluxed using wax. got a lot of dirt and gunk out of it or course. Now I have melted down my first ingots for casting. Melted it down and fluxed just at the start. I got what I can only describe as fluff. It reminded me of when you boil food too hot and get this fluff on the top... make sense?

Anyway, it didn't appear 'dirty' by sight, but it didn't stir back in easily so I scooped it off. Is that the right thing to do or should I put it back in on the next casting session? What I don't know is did I remove anything I need or is this just gunk to be disposed of? FWIW the pot was just at melt temp so it wasn't super hot.

Many thanks

Did this gunk have any weight to it when you skimmed it off? If it did, it is probably tin oxide.

Next time you fire up the pot to cast, add this back to the pot and use something like sawdust for flux. when the alloy comes up to temp, use a paint stick or the back of a spoon to rub the dross against the sides of the pot and see if it melts back into the alloy.

I have the best luck when casting to leave a layer of carbon ash on top of the melt. This helps prevent the lighter metals from oxidizing out of the alloy. Plus, the layer of carbon ash will help keep the sides and metering rod clean.

If you are ladle casting, you will have to work around the layer of ash.

My 2¢

[Charlie Two Tracks]

I haven't done a whole lot of casting Markbo, but I did try the sawdust flux (as recommended by these guys) and it worked great. I have a bottom pour and leave about 1/2 inch of burned up sawdust on top at all times. It helps insulated the pot also but the big advantage is that when I pull back some of the carbon, it is shiney silver lead that I see. This is a great place to learn stuff.

[runfiverun]

greyish black fluff.
dirt like.
chuck it.
heavy weight silverish re-smelt it.
i keep all the scrapings from the casting pot that are silverish and do the flux/burn in the smelting pot.
you get some good stuff back, but gotta chuck a lot of fluff to get to it.

[Markbo]

Hmmmmmmm.... I am going to test the few bullets I saved for hardness before and after removing that to see if there was any change. I will put it back in the next pot and flux over again. So far I have only been using wax and a few drops of oil. Guess I need to make some sawdust! :smile:

[lwknight]

can only describe as fluff. It reminded me of when you boil food too hot and get this fluff on the top... make sense?

Thats exactly what zinc does. The floaty oatmeal looking stuff is not something you want. If it is in fact zinc , you will get some froth everytime you melt it. It will still cast and may cast very well. A little zinc in lead makes it really hard.

[EMC45]

I put a WW in my pot this weekend while casting. Like an idiot I didn't double check the stampings on it. It was ZINC!!! It made my melt all "frothy" on top and it WOULD NOT blend back in. I empty the pot and then scooped out all the Zinc. It was light and it looked very grainy coming out. After I emptied the pot I put the ingots that I poured from the pot back in and they finally blended back together. What a pain!! That is the first time that has ever happened!!!!

[lwknight]

Only a small percentage of zinc will alloy/blend with lead. Possibly some tin would help stabilize the zinc like it does antimony. Just guessing. The only experience with zinc was small experimental batches. Just keep tossing the funky stuff out and it will make a good alloy eventually but , the remaining zinc will age harden.

I poured some zinconated lead out in puddles. At first they would bend like pure lead. Then after a few weeks they would not bend. In fact if forced they would snap.
Even very thin narrow puddles would not be bent/broken by hand. I used a vice and hammer to try to unbend what was bent when soft and it just broke instead of unbending.

[Markbo]

Here is a pic of the dross in question:
http://i116.photobucket.com/albums/o10/Markbo_photos/Reloading/Castbullets10-20-2010004.jpg

I placed a bullet cast from that pot to compare the color. You can see the bullet is more silver, as is a small amount of drip at the top of the photo. Most of this stuff is just gray. All the tiny black dots appear to be ash or something... they are not air holes. It is fairly hard, but not super. I obviously don't know for sure but I kind of doubt it's zinc simply because when I smelted all the WWs down, I spooned everything out of it long before it got too hot.

It could be of course... I just don't think so. Next attempt, I will add another ingot (only about 3 in the pot at the moment and add this stuff back to it, trying a handful of sawdust insteda of wax to see what happens.

ETA: I tested several before and after bullets and they all came out under 8 bnh using my Lee tester! I think they are a little on the soft side, no?

[rattletrap1970]

I keep my smelting pot "JUST OVER" the melting point of wheel weights. I've had Zn weights and Fe weights floating in the lead for a while, then scooped them out whole. I just got done melting over 150 lbs or lead and poring into ingots and I've had no issues with Zn melting in.

[EMC45]

That's what mine looked like over the weekend. It was all fluffy and light. It will go to the trashcan.

[epj]

I've never had anything that looked quite like that stuff. I do have a certain amount of shiney stuff in the dross that is probably tin I need to get stirred in better.
Your boolit looks like the edges are rounded in the photo. If that is indeed the case, your alloy needs more tin to get proper fill out.

[ghh3rd]

I read a thread in this forum about using Sulphur to remove Zinc from contaminated lead:
"Zinc Removal with Sulfur Report" http://castboolits.gunloads.com/showthread.php?t=63082

May be worth reading if you have much contaminated lead.

Randy

[runfiverun]

re-test the bhn in a few days.

you need more heat in your mold.

zinc is soluble in lead alloys up to 1.6% or thereabouts and adds hardness.
that dross looks more like kirksite. or like zamac pewter [not really pewter]
zinc is more bubbly but is about that silverish in color, antimony is a more grey/black undertoned flat color, that mimics zinc and is easily fluxed back in with a higher heat.

[Bret4207]

Never seen anything like that before.

[Markbo]

That bullet is a throw away. I put it in there just for color comparison. It was an early drop from a too cool mold and they got better the hotter it got.

BTW that 'fluff' is not light. It looks like foam, but it has some weight to it. Since my BNH is so low I am going to try to mix it back in another batch and flux like crazy to see if it mixes back in. if not, I'll throw it out and add a touch of tin solder for hardness I guess.

[runfiverun]

i'd try melting it at 700* all by itself first and see what drops out.
zinc will pull tin out of an alloy.