Removing surface lead from brass.

This is completely from John Palmer off the Realbeer website

(http://realbeer.com/jjpalmer/Welding.txt)



<start>"Brass is an alloy of Copper and Zinc with some lead thrown in for

machinability. The lead percentage varies, but for the common brass alloys

used in plumbing fittings it is 7% or less. Lead is entirely soluble in

copper, but the presence of zinc changes this. In Brass, the lead exists as

minute globules. These globules act as an intrinsic lubricant during

machining. The result is a micro-thin film of lead being smeared over the

machined surface. It is this lead (a very small amount) that can be

dissolved off by the wort. While this small amount of lead should probably

not be a cause of concern, most people would be happier if it wasn't there

at all.



Well, never let it be said that the Space Program never yields technology

applicable to the home. Some chemists working on the International Space

Station Alpha program were consulted for an etchant that could safely remove

the lead from the surface of brass parts. The chemists determined that a

1-to-1 volume ratio of Glacial Acetic Acid (98% by vol.) to Hydrogen

Peroxide (30% by vol.) would accomplish this without pitting the brass. This

procedure was performed in the lab using the standard laboratory

concentrations of these chemicals. The process consisted of a 30 second

dunk, swirl and rinse at room temperature, and was successful in removing

the lead, as determined by a Lead Home Test Kit (swabs). In addition, the

procedure had the added benefit of turning the brass into Pure Gold. (Okay,

the color of, anyway.)



Because 98% Acetic Acid and 30% Hydrogen Peroxide are not available to the

average brewer, the experiment was repeated using the concentrations

available in the supermarket. These are 5% Acetic Acid (White Distilled

Vinegar) and 3% Hydrogen Peroxide. Due to the difference in concentration,

the relative concentration ratio is changed. For the household variety

concentrations, a 2-to-1 volume ratio of Acetic Acid to H2O2 is needed.



The process was expected to take longer with the more dilute solution, so

the brass part was immersed for 10 minutes. The results showed the same gold

color and the Lead Test swab indicated the lead had been removed. The

buttery yellow gold color can be used as an indicator that the process has

completed. Home Lead Test kits should be available at most hardware stores.



This procedure for removing surface lead from brass can easily be conducted

at home. A 10-15 minute dunk, swirl, and rinse in a 2/1 volume ratio of 5%

Acetic Acid and 3% Hydrogen Peroxide has been shown to be effective. By the

way, the solution can be irritating to the skin so either wear gloves or use

tongs."<end>

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John Palmer also addresses this in his "How to Brew" on-line book

(www.howtobrew.com) in Appendix B under cleaning copper.

