This is the Gaddy Formula which works very well and excludes inactive chemicals:
Rust Bluing Formula per Oscar Gaddy Stock Solution; dilute 1:1 … and up to 1:8 for final rustings. To make 125 ml Stock Solution:
Conc. HNO3 ..... 3.22 ml
Hg2Cl2 (Mercuric chloride -- DEADLY poison) .... 6.25 gms
C2H5OH ..... 3.25 ml
Fe2Cl3 ..... 5 ml
H2O ..... to make 125 ml
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Parker Factory Process Adapted by Oscar Gaddy: (DGJ 1997 #2, #3 & 2003 #1)
1. Prep as in Oscar’s original process [next page], Steps 1 – 7
2. “Light” Etch in “mild” Fe2Cl3 solution [I used 15%, it was hard to maintain even results in hi ambient temps of FL – Oscar later moved down to ~ 10%, some report using 7.5%]
3. Rust and card once daily, for 7 to 10 days, as in Oscar’s original process, but no boiling (wet card?) [I dry carded with 0.006 wire wheel, need to check speed, 0.005 or .004 better]
4. Only after 7 to 10 passes, plug bores with rubber stoppers (one in each bore with stainless, ¼,” 90 o degree-bent tube for pressure relief), then boil 5 minutes, in solution of 3.5 ltrs water with 60 cc logwood powder + 30 cc FeSO4 . 7 H2O powder (copperas)
5. Rinse well in cold water
6. Soak ~ 5 minutes in solution of ~ 3.5 ltrs water with 15 cc FeSO4 powder (concentration not critical) – a finger should be able to rub to show light metal with contrast
7. Scrub with CaCO3 powder picked up on wet towel (paper or cloth)
8. Job should look good, but can be improved if desired by rusting and carding 2 or 3 more times; if that is done repeat final steps 4 thru 7. [Parker factory on notes 2nd following page]
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