Linotype way to HOT

[altheating]

The other night after working way too many hours I got home, plugged in my old Lyman pot, showered ate supper and went straight to the loading room to begin casting with my new NOE 225107 37gr Hornet mold. As soon as the lead was melted I gave it a quick fluxing and began to cast. The mold started right out casting beautiful boolits. I added a bit more lino and after about 200 more of these little jewels I noticed the bullets getting greyish in color. Not yet realizing that I had the heat setting that high, I drained the pot of all the lino. The pot was refilled with more lino and I resumed casting. I then realized the pot was set way to hot. I adjusted the temp and all was fine.
My question is this, do I have to handle the overheated lino differently in order for the alloys to mix properly or can I just add it to the mix in the pot, flux and cast? Not sure if the materials separate beyond use (I'm guessing not) at the high temps.

By the way that is one sweet mold.

PS - Lesson learned, no casting when I have been awake for 18 hours and working on 4 hours sleep!

[plainsman456]

You shouldn't have to handle it any different from the lino you cast second.

[DukeInFlorida]

The condition that you mention (grayish) sounds a lot like what we call, "FROSTED BULLETS".... What most likely causes it is the lead sticking to the mold as you pulled the halves apart. The mold would pull up microscopic peaks, giving the bullet a gray textured look. If you had allowed the bullets to cool in the mold more (inverting the mold, and allowing the sprue cutting plate to rest on a cotton towel, moistened with water, would have cooled it faster), the bullets would have come out as shiny as normally they would.

The same happens with other lead alloys (WW, 50-50, etc)........... That's why some guys buy multiples of a mold. They allow one to cool while they are filling the other one. Each mold/bullet has a different cooling rate, and you can only go as fast as the mold/bullet/temperature of the lead will allow.

[geargnasher]

The condition that you mention (grayish) sounds a lot like what we call, "FROSTED BULLETS".... What most likely causes it is the lead sticking to the mold as you pulled the halves apart. The mold would pull up microscopic peaks, giving the bullet a gray textured look. If you had allowed the bullets to cool in the mold more (inverting the mold, and allowing the sprue cutting plate to rest on a cotton towel, moistened with water, would have cooled it faster), the bullets would have come out as shiny as normally they would.

The same happens with other lead alloys (WW, 50-50, etc)........... That's why some guys buy multiples of a mold. They allow one to cool while they are filling the other one. Each mold/bullet has a different cooling rate, and you can only go as fast as the mold/bullet/temperature of the lead will allow.

The only issue with overheating Linotype is that it drosses excessively on the surface at temps much above 725F, and the oxides are heavy on the tin and antimony compared to lead, so if you skim this dross off and discard it rather than using sawdust or wax to reduce these oxides back into elemental metals, you will gradually deplete the lino of it's precious additives.

I disagree with the above explanation of "frosty" boolits. First, it isn't caused by a too-hot alloy being poured into the mould, it's caused by an overheated mould as a result of casting too fast for the alloy temperature. The solution is to reduce the pot temperature to 100 degrees over full liquidus and cast at a rate that gives the finish the caster desires, usually shiny or light satin frost with any alloy containing antimony. Now, on to the frosting. After reading a bit in the Metals Handbook and learning about Dentrites, it seems that any alloy containing more antimony than tin, but less than 12% antimony, will push some pure antimony crystals to the surface of the alloy, breaking through the surface tension of the lead. Due to the nature of the phase changes and order of freezing between Pb, Sb/Sn intermetallic, and free Sb (there is no free tin because it all combines with Sb to form Sb/Sn unless there is more tin than antimony), the free Sb solidifies first and, since it is a smaller molecules, gets wrung out of the slush like water from a wet sponge as the remainder of the constituants of the boolit continue to cool and solidify. When the mould is very hot, too hot for casting, the effect of the primary phase becoming solid and creating grain formation that is visible on the surface (in truth it forms throughout the boolit, making it very brittle) is greatly amplified.

Notice also that true eutectics, like linotype that is proportioned EXACTLY correctly and has not been depleted of any tin or antimony to change the proportions, cast very shiny boolits because all of the elements present are in such proportions that they all freeze together, at the same time and same temperature, like a single, pure metal would. 63/37 solder does this, too, it has no "slush" or "mush" phase, just solid and liquid. The fact that it freezes all at once minimizes the dentrite growth since there is no primary phase of solidification taking place within the liquid. While even pure linotype will form a "frost" when the mould is hot enough, but it has to be much hotter than a non-eutectic Pb/Sb/Sn alloy to do so.

Gear

[williamwaco]

I don't like linotype because it is way too hard for my uses but It does make beautiful bullets. When I do use it, I find it is much "thinner". It flows like water, faster and easier than any other bullet alloy I have ever used. It is designed for casting type - individual letters the size of these you are reading. It really fills out every nook and cranny in the mold.

It also does this at significantly lower temperatures than normal bullet alloys. I don;t have a thermometer but I turn my rheostat down from 6 to 5 on my Lee pot when casting linotype.

[geargnasher]

Lino melts at 464F. It also freezes at 464F. Most of the clip-on wheel weight alloy I've cast with is fully molten at somewhere between 550-580F. Basically you can run the pot 100 degrees cooler with straight lino.

Gear

[DukeInFlorida]

Thank you for setting me straight!! Makes perfect sense!

So much to learn................


The only issue with overheating Linotype is that it drosses excessively on the surface at temps much above 725F, and the oxides are heavy on the tin and antimony compared to lead, so if you skim this dross off and discard it rather than using sawdust or wax to reduce these oxides back into elemental metals, you will gradually deplete the lino of it's precious additives.

I disagree with the above explanation of "frosty" boolits. First, it isn't caused by a too-hot alloy being poured into the mould, it's caused by an overheated mould as a result of casting too fast for the alloy temperature. The solution is to reduce the pot temperature to 100 degrees over full liquidus and cast at a rate that gives the finish the caster desires, usually shiny or light satin frost with any alloy containing antimony. Now, on to the frosting. After reading a bit in the Metals Handbook and learning about Dentrites, it seems that any alloy containing more antimony than tin, but less than 12% antimony, will push some pure antimony crystals to the surface of the alloy, breaking through the surface tension of the lead. Due to the nature of the phase changes and order of freezing between Pb, Sb/Sn intermetallic, and free Sb (there is no free tin because it all combines with Sb to form Sb/Sn unless there is more tin than antimony), the free Sb solidifies first and, since it is a smaller molecules, gets wrung out of the slush like water from a wet sponge as the remainder of the constituants of the boolit continue to cool and solidify. When the mould is very hot, too hot for casting, the effect of the primary phase becoming solid and creating grain formation that is visible on the surface (in truth it forms throughout the boolit, making it very brittle) is greatly amplified.

Notice also that true eutectics, like linotype that is proportioned EXACTLY correctly and has not been depleted of any tin or antimony to change the proportions, cast very shiny boolits because all of the elements present are in such proportions that they all freeze together, at the same time and same temperature, like a single, pure metal would. 63/37 solder does this, too, it has no "slush" or "mush" phase, just solid and liquid. The fact that it freezes all at once minimizes the dentrite growth since there is no primary phase of solidification taking place within the liquid. While even pure linotype will form a "frost" when the mould is hot enough, but it has to be much hotter than a non-eutectic Pb/Sb/Sn alloy to do so.

Gear

[altheating]

Thanks for the info folks. The gray boolits will be the first to disappear tomorrow morning. Going to find out how them little buggers shoot!

I forgot to mention that just after those boolits cooled enough to dump them out of the mold I pressed on them with a flat screwdriver blade and they literally turned to dust. They were way to hot. I've seen frosted boolits before, these were way beyond slightly frosted. Anyway, it was a learning experience.

[1Shirt]

Just my 2 cents, but am of a similar mind with Gearnasher!
1Shirt!:coffee:

[geargnasher]

The frosty boolit thing really made sense to me when I cast a series of boolits starting with a room temperature mould and cast as fast as I could until the boolits looked like they had been sandblasted. I did this three times, once with the pot temperature equalized at 800, then at 700, then at 600 degrees. What I found was that you can cast shiny, wrinkled, rounded, half-filled boolits with 800 degree wheel weight metal if your mould is too cold. You can also cast grainy, hyper-frosted, crumbly disasters with 600-degree metal if the mould is hot enough. So pot temp has nothing to do with it, mould temperature does. Also, if you look at the surface of a really frosted boolit with a 50X microscope, you can see the grain formation on the surface, and it isn't characteristic of stippling from adhesion, it's more like a pattern of tiles.

Gear

[altheating]

I added to overheated Lino back into the mix yesterday. No problems at all. Thanks for the advise.