I am producing Iron Oxide with the intention of using it for pigmentation. My attempts so far have been to use electrolysis. My first attempt I used Borax as an electrolyte and a 12 volt adapter with 3-4ish amps. The result was a typical light orange rust color, however the process was rather slow, 24 hours resulted in about a tablespoon of rust. My next attempt I used table salt instead. This was far faster, it produced nearly a cup of black sludge in 10 hours. As per the tutorials I watched on youtube, I then filtered the matter through a coffee filter and a funnel, then heated the result in a pan. The result however was a rust color covered in a layer of black crust, as if I had burnt a sheet of cookies. Powdering the result gave me a powder of very dark brown color.The Residue left over on the coffee filter and in the container I used for electrolysis are the typical rust orange color I would expect. It is my understanding that heating the black matter that results from the electrolisis usually produces a more red color. So my question(s) are:

  • how I can change my approach to produce red pigmentation using this process, and why may I have ended up with black residue instead of orange or red?
  • What are the variables that change the pigmentation of rust?
    • Is it the speed at which it drys? the temperature in which it is heated? the electrolyte used in the process of electrolysis?
  • $\begingroup$ Because I like to do things myself. And I like to learn how these things work. I Also have access to a lot of old scrap iron. Honestly this is a silly question. I'm an artist and I like to make things from scratch, why do anything I do? why build myself a kitchen island from wood I logged and milled from the forest when I could just buy one from lowes? Does it really matter why I want to do it this way? $\endgroup$ Jul 14, 2022 at 19:03
  • $\begingroup$ I'll try ball milling it and see how that changes the pigmentation. Thank you for the suggestion, I will let you know how it goes $\endgroup$ Jul 14, 2022 at 19:32

1 Answer 1


Red iron oxide is Fe2 O3 , it forms in air at roughly 700F. In a water solution you will make "rust", brown/red. Rust is a complex mixture of hydroxides and hydrated oxides such as Fe3 O4 -H2O. At temperatures higher than 700 F you start getting black Fe3 O4 ( aka mill scale). At very high temperature you get black Fe O. Fretting corrosion will produce Fe2 O3 at room temperature but is not a practical source.

  • $\begingroup$ What IS a practical source? $\endgroup$ Jul 26, 2022 at 16:03
  • $\begingroup$ On the net I find "red ochre" is mostly Fe2 O3 made by roasting mixed iron oxides but no specific information. $\endgroup$ Jul 26, 2022 at 16:40

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