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Showing results for tags 'blackening'.
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Hi Folks, I want to start this with a disclaimer. I AM A NOVICE IN THIS AVOCATION AND HAVE LEARNED EVERYTHING I KNOW (or don't) THROUGH EXPERIMENTATION AND MSW. I've read a lot of posts over the last few years about people having problems with chemical blackening of brass. After a a lot of trial and error I've had a lot of recent success. I've using Birchwood Casey Brass Black, Acetone, and Sparex. I first take any brass I want to blacken and soak in acetone for 5-10 minutes to remove any solder flux, lacquer, or finger prints. I've taken a small piece of window screening and pushed it into a steel can (tomato sauce) to strain the solutions and the pieces being blackened. I make a solution of Sparex (acidic pickling) by putting warm water (125-130 degrees) in a glass container. Add the dry Sparex in an amount greater than recommend. After 15 minutes or so stirring the mixture with a piece of wood, pour off the liquid into a jar with a cover leaving the undisolved Sparex behind. You now have a saturated pickling solution. Taking the pieces to be blackened out of the acetone, place in the warm Sparex solution for about 10-15 minutes. Keeping the Sparex warm makes it work faster, but you can use it cold, just give it more time. You should take the pieces to be blackened out of the Sparex and rinse under cold running water, but I just put into a jar with water and shake vigorously. I then strain into to the can with the screening. I make a solution of Brass Black to water of 1:7.5. I use a paint pipets, but any way is fine. After taking the rinsed pieces out of the water I place them in the diluted Brass Black. I then watch them carefully until mostly black. I then remove, strain, and rinse vigorously then returning them to the blackening solution. I will generaly do it twice more, following the same process rinsing after each immersion. I then place on a paper towel to dry for a couple of days. By following this routine I've gotten deeply blacked pieces without having any of the blackening rubbing off and making a mess of my hands and everything else. Now here comes comes the chemistry question for all my brilliant colleagues out there. I would much rather darken the pieces with one longer immersion in the blackening solution. But when I do that, the blackening flakes and gets everywhere making a mess. I've been thinking about being a small kid in my Grandfather's darkroom. As I've alluded to, I am dolt as far as chemistry is concerned. But in a process in developing film and prints, my Grandad would talk about the "Fix" which, I understood was the chemical which stopped the development process. Given my limited understanding, Brass Black and other blackening processes involve an acidic solution. Therefore, would a immersion in a base, like a baking soda solution, "fix" the reaction and allow for one blackening run as opposed to a number? I'll try some more experiments and let everybody know if I have a "Eureka" moment, but in the interim, would certainly appreciate any corrections, feedback, or other comments. Best, John
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I received some Jax Pewter Black on Friday. I wanted to give it a try to see if it was better than Birchwood Casey Brass Black. So I did an experiment this afternoon and I'm pretty horrified by the results. Maybe I'm doing something wrong. Here's what I did - I cut some small strips of brass. On one side, I sanded them, then wire brushed them to make sure they were absolutely clean. I left the other side uncleaned to see if it made a difference. Then I soaked half of the pieces in white vinegar and the other half in diluted muriatic acid for 10, 5, & 1 minute plus I left two control pieces that were not soaked in any acid. When I put some of the pieces in the Jax (full strength) they turned brown rather than black. After about 2 minutes, I removed them and rinsed them with tap water. The brown coating flaked right off! So I put them back in for 5 minutes. When I took them out and rinsed them again, there were a few spots that had some of the brown sticking to them but the pieces looked very splotchy - both on the sanded and unsanded side. I could never use those parts on a model. I also decided to try the Jax diluted 50-50 with water and left the pieces in for 10 minutes. Equally bad results. Splotchy, brown, & ugly. They looked more like copper than iron. The acid used appears to make no difference and I can't see that the soak time does either. Diluting the Jax didn't seem to have any effect one way or the other. I'm very disappointed and this stuff was not cheap ($25). I'd be glad to have any tips on how I might do something different to achieve better results. For now, I'll be going back to Birchwood Casey, but it's a shame to have to toss out this expensive bottle of stuff since it seems to work for others. Like I say, maybe I'm doing something wrong but I can't think what it would be. Thanks - John
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