The Making of Rouge
High quality Rouge polishing compound can be made by heating Ferrous oxalate Dihydrate, C2FeO42H2O. Buy a pure grade of it as the quality of the Rouge will depend on the quality of the Ferrous oxalate. The grade I used was more than 98% pure. Place the powder in a very clean flame resistant pan and heat it with a strong gas flame. It must be done in a well ventilated room since a lot of carbon monoxide vapours will come off and it will be a good idea to wear a gasmask. Wait till parts of the yellow powder starts to turn dark brown and then start to mix it slowly with a spatula or similiar instrument. During the mixing carbon monoxide will be seen bubbling up from the powder. Eventually all the powder will turn dark brown. Thereafter the powder will starts to turn red brown where the reaction with the oxygen in the air has been completed. During mixing at this point parts of the powder will glow and then die down when the reaction has been completed. Continue to slowly mix the powder until all the powder has turned red brown. Wait a few minutes to make certain that all the powder has been converted to rouge before turning off the gas flame.[1]
Rouge is actually just a very pure form of red iron oxide or what we more commonly know as rust. Rouge is the French word for red. Rouge has a slower action as for example Cerium oxide which makes it more suitable for the final corrections to be made on optical work. When an optical piece is very near to form one wants to make very small corrections but with a fast acting polishing compound too much correction might be made.
Photos
Here is a few photos of the rouge making process:
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| The yellow powder before heating. | The powder starts to turn dark brown after a few minutes. | The red brown rouge when the reaction is finished. |
References
1. Texereau, Jean. How to Make a Telescope, 2nd English edition, Willmann-Bell, 1984.