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Thread: A question for you math wizards.

  1. #1
    Boolit Man
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    A question for you math wizards.

    I have certified 16-1 casting material. I would like to mix a small batch at 20-1. How much pure lead should I add to 10 lbs. of the 16-1 to make 20-1?
    Thanks in advance!
    JKR

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    2 lbs.

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    Boolit Master hoodat's Avatar
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    I can't believe I even opened a thread with that title. jd
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  4. #4
    Boolit Buddy
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    Your 10 lbs (160 oz) of 16:1 will contain 9.41 oz of tin (160/17).

    Converting that tin to 20:1 mix will give you 197.6 oz total (9.41 x 21).

    Deduct the original 10 lbs (197.6 - 160 oz), leaves 37.6 oz of additional lead - two and a bit pounds.
    Last edited by Wilderness; 11-06-2022 at 05:31 PM.
    It'll be handy if I never need it.

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  5. #5
    Boolit Master
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    Okay, so the THEAD TITLE is a little "counter intuitive" (for me), too, but I got an answer I believe in. Using the
    (PbConcentration1)(AlloyWeight1) = (PbConcentration2)(AlloyWeight2), I got that 2.357 pounds of .999 Pb is needed to make 20:1 Pb:Sn alloy:

    (PbC1)x(AW1)=AW2. (.5882 x 10)/.476 = AW2 = 12.357.
    (PbC2)

    Subtracting 10 lbs (W1) from the final weight desired (12.357) for the alloy leaves 2.357 lbs lead required to increase 10 pounds of 16:1 Pb:Sn to 20:1 alloy

    2.357 pounds works out to 2 pounds 5.25 ounces. If your specs demand EXACTLY 20:1 alloy, this is the amount to make 20:1 alloy out of 10 pounds of 16:1. I 20:1 is more of a "best recommendation", I think I might add pure Pb in 12 oz. portions, cast, then try.
    Last edited by Kosh75287; 11-06-2022 at 06:07 PM. Reason: Spacing in equations
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  6. #6
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    Just download the alloy calculator available on the forum and use it!
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  7. #7
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    16 - 1 equals 93.75% lead, 6.25% tin so in ten pounds you have .625 of a pound of tin in your 16-1 alloy. The amount of tin will not change when you add more tin.

    20 - 1 equals 95% lead, 5% tin

    You have .625 pounds of tin so you will have to add 2 1/2 pounds of lead to your 10 pounds to get the tin down to 5% (20-1).

    .625 divided by 12.5 equals 0.05. Convert to % you multiple by 100 which equals 5%
    Last edited by M-Tecs; 11-06-2022 at 08:18 PM.
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  8. #8
    Boolit Buddy
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    Quote Originally Posted by Kosh75287 View Post
    Okay, so the THEAD TITLE is a little "counter intuitive" (for me), too, but I got an answer I believe in. Using the
    (PbConcentration1)(AlloyWeight1) = (PbConcentration2)(AlloyWeight2), I got that 2.357 pounds of .999 Pb is needed to make 20:1 Pb:Sn alloy:

    (PbC1)x(AW1)=AW2. (.5882 x 10)/.476 = AW2 = 12.357.
    (PbC2)

    Subtracting 10 lbs (W1) from the final weight desired (12.357) for the alloy leaves 2.357 lbs lead required to increase 10 pounds of 16:1 Pb:Sn to 20:1 alloy

    2.357 pounds works out to 2 pounds 5.25 ounces. If your specs demand EXACTLY 20:1 alloy, this is the amount to make 20:1 alloy out of 10 pounds of 16:1. I 20:1 is more of a "best recommendation", I think I might add pure Pb in 12 oz. portions, cast, then try.
    Kosh - I wondered about the discrepancy between calculations - mine 2 lb 5.6 oz calculated on one decimal place, to your 2 lb 5.25 oz. Found it - .357 lbs x 16 oz is 5.7 oz. Near enough.

    We need to be careful about ratio definitions too - 16:1 is 16 parts lead to one of tin, not one part tin in 16 total. I presume the commercial alloy really is 16:1, not one part in 16.
    Last edited by Wilderness; 11-06-2022 at 07:41 PM.
    It'll be handy if I never need it.

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  9. #9
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  10. #10
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    When I first read this post I got a pencil and piece of paper took off my shoes and socks getting ready to do some serious counting but decided to go take a nap instead , I'm glad I did ....
    I would just drop 1 big muffin ingot of plumbing lead in the pot

  11. #11
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    I vote for 2.5 pounds
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  12. #12
    Boolit Master
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    Quote Originally Posted by M-Tecs View Post
    16 - 1 equals 93.75% lead, 6.25% tin so in ten pounds you have .625 of a pounds of tin in your 16-1 alloy. The amount of tin will not change.

    20 - 1 equals 95% lead, 5% tin

    You have .625 pounds of tin so you will have to add 2 1/2 pounds of lead to your 10 pounds to get the tin down to 5% (20-1).
    thats what I got - not sure its right - remember our numbers are ratio so 16:1 is 17 parts total - 20:1 is 21 parts total
    He has 10 pounds of a 16:1 alloy so divide 10/17 = .588 pounds tin ----.588 x 20 gives 11.76 pounds - (pure lead) now add in the tin? + the .588 pounds tin comes to a total of 12.348 pounds total -- so add 2.348 pounds pure lead

  13. #13
    Boolit Master
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    Quote Originally Posted by toallmy View Post
    When I first read this post I got a pencil and piece of paper took off my shoes and socks getting ready to do some serious counting but decided to go take a nap instead , I'm glad I did ....
    I would just drop 1 big muffin ingot of plumbing lead in the pot
    Yep me too - then scratch a couple boolits with a pencil to see what change we got

  14. #14
    Boolit Master
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    This stuff sounds simple but is quite tricky if we wanna get technical - much depends on what is writ and how that is interpreted
    my take - tell me you are using a Ratio of 16:1 says 16 parts lead to one part tin ....total is 17 parts
    tell me one part tin in 16 and I get a different message - that is saying 16 pounds in the pot of which one pound is tin - so a 15:1 ratio?

  15. #15
    Boolit Buddy
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    Greetings,

    Using the downloadable Alloy Calculator, I get 10 pounds of 16-1 plus 2.25 pounds Pure Lead = 12.25 pounds of 20-1.

    Cheers,

    Dave

  16. #16
    Boolit Grand Master



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    Quote Originally Posted by indian joe View Post
    thats what I got - not sure its right - remember our numbers are ratio so 16:1 is 17 parts total - 20:1 is 21 parts total
    He has 10 pounds of a 16:1 alloy so divide 10/17 = .588 pounds tin ----.588 x 20 gives 11.76 pounds - (pure lead) now add in the tin? + the .588 pounds tin comes to a total of 12.348 pounds total -- so add 2.348 pounds pure lead
    You and Kosh75287 are correct. I overlooked the part total of 17 parts affecting the actual percentage. 94% lead 6% tin.
    2nd Amendment of the U.S. Constitution. - "A well regulated Militia, being necessary to the security of a free State, the right of the people to keep and bear Arms, shall not be infringed."

    "Before you argue with someone, ask yourself, is that person even mentally mature enough to grasp the concept of different perspectives? Because if not, there’s absolutely no point."
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  17. #17
    Boolit Buddy
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    Quote Originally Posted by fc60 View Post
    Greetings,

    Using the downloadable Alloy Calculator, I get 10 pounds of 16-1 plus 2.25 pounds Pure Lead = 12.25 pounds of 20-1.

    Cheers,

    Dave
    Dave - something wrong there. 10 lbs 16:1 (160 oz) divided by 17 gives 9.41 oz of tin. 12.25 lbs (196 oz) of 20:1 divided by 21 gives 9.33 oz of tin. Looks like we lost some tin in the remix.
    It'll be handy if I never need it.

    Insomniac, agnostic, dyslectic - awake all night wondering if there is a Dog.

  18. #18
    Boolit Master
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    Quote Originally Posted by Wilderness View Post
    Dave - something wrong there. 10 lbs 16:1 (160 oz) divided by 17 gives 9.41 oz of tin. 12.25 lbs (196 oz) of 20:1 divided by 21 gives 9.33 oz of tin. Looks like we lost some tin in the remix.
    tin didnt go missing ----add 2.348 pounds of lead and the numbers will come right.

  19. #19
    Boolit Buddy
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    Quote Originally Posted by indian joe View Post
    tin didnt go missing ----add 2.348 pounds of lead and the numbers will come right.
    Joe

    Yes, 2.348 lbs = 2 lbs 5.6 oz, my original calculation.

    I was pointing out a possible error in the Alloy Calculator.

    I am glad we are not building a bridge.
    It'll be handy if I never need it.

    Insomniac, agnostic, dyslectic - awake all night wondering if there is a Dog.

  20. #20
    Boolit Master
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    Quote Originally Posted by Wilderness View Post
    Joe

    Yes, 2.348 lbs = 2 lbs 5.6 oz, my original calculation.

    I was pointing out a possible error in the Alloy Calculator.

    I am glad we are not building a bridge.
    I am still in favour of the "chuck another muffin pan nugget in an she'll be right mate"

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