Craftsman Style Blog

How to bleach orange shellac and problems encountered.

Moheb Maher asks about bleaching orange shellac.

Dear Sir,

I’ve tried to bleach shellac following this procedure :

1- I dissolved 5gm sodium carbonate in 300 ml cold water to get an alkaline medium.
2- I heated this aqueous alkaline solution to 90 C.
3- I dissolved 30 gm orange shellac in that solution.
4- I dissolved 10 gm of sodium hypochlorite in 200 ml hot water, and stirred until I could smell the odor of chlorine gas.
5- I mixed the two solutions when they got cold.
6- The color of shellac has been bleached, and the solution became milky “light beige”.
7- I recovered the shellac from that solution by adding some sulfuric acid.
8- A milky white precipitate has formed immediately.
9- I washed the precipitate, and filtered it. “This precipitate should be bleached shellac”.
10- I left the filtered powder to dry, then tried to dissolve it in ethanol.
11- Surprisingly the precipitate did not dissolve?

Would you please advise me where is the problem?

Thank you very much,
Regards,
Moheb.