Are diamonds able to go in the Silver Blackener? The Jax Silver Blackener will NOT hurt your diamonds. Everyone blackens silver with the diamonds in place. Post navigationPrevious post: We are a jewelry company that had to pull back on cleaners due to harsh chemicals/safety of employees, and are interested in a fast tarnish remover. Can you tell me what’s in the Jax Instant Silver Cleaner and the Jax Silver Polish? Or if you can’t be specific, are there any hazardous waste materials involved?Next post: I have brass knobs in my house from the 40s that look like dark copper. I also have newer bright shiny lacquered brass doorknobs that I hate. I am hoping to remove the lacquer and darken the modern doorknobs to match. Which darkening color would you recommend? Black, Brown-Black or Brown?