Bismuth dye system for human hair

1. A hair dyeing composition which comprises the following ingredients:

(a) from 0.1 to 5 wt % of a bismuth salt;

(b) from 0.1 to 5 wt % of a thiosulfate compound;

(c) from 1 to 20 wt % of a delta-valerolactam;

(d) from 0.25 to 2.5 wt % of an alkaline agent;

(e) from 0 to 5 wt % of elemental sulfur and

(f) from 50 to 90 wt % of water.

2. A hair dyeing composition as defined in claim 1 which also includes an alkaline material selected from the group consisting of ethanolamine and triethanolamine.

3. A hair dyeing composition as defined in claim 2 which includes a surfactant.

4. A hair dyeing composition as defined in claim 3 where the surfactant is selected from the group consisting of ethoxylated phenols.

5. A hair dyeing composition as defined in claim 3 which contains from 0.1 to 5 wt % of elemental sulfur.

6. A method of catalyzing a bismuth salt-thiosulfate containing hair dye, said method comprising adding to said hair dye an effective amount of delta-valerolactam.

7. A method of dyeing human gray hair, said method comprising applying a composition comprising:

(a) from 0.1 to 5 wt % of a bismuth salt;

(b) from 0.1 to 5 wt % of a thiosulfate compound;

(c) from 1 to 20 wt % of a delta-valerolactam;

(d) from 0.25 to 2.5 wt % of an alkaline agent;

(e) from 0 to 5 wt % of elemental sulfur; and

(f) from 50 to 90 wt % of water.

8. A method as defined in claim 6 where the composition also includes a surfactant.

9. A method as defined in claim 6 where the composition also includes from 0.1 to 5 wt % of elemental sulfur.

10. A hair dyeing composition which comprises the following ingredients:

(a) from 0.1 to 5 wt % of a bismuth salt;

(b) from 0.1 to 5 wt % of a thiosulfate compound;

(c) from 1 to 20 wt % of a delta-valerolactam;

(d) from 0.25 to 2.5 wt % of an alkaline agent;

(e) from 0.1 to 5 wt % of elemental sulfur and

(f) from 50 to 90 wt % of water.