community of dyers

It's a two-step process. Exhaustion is when the dye leaves the water for the fiber, which is a process whose results you can readily see. That's the first step. The second step is when the dye in the fiber forms bonds to it, mainly hydrogen type bonding in the case of the acid dyes, and covalent bonding in the case of the reactive dyes.

Bonding between the Lanaset dye and the protein fiber cannot occur without exhaustion of at least some of the dye. It has to be next to it in order to bond to it (obviously). However, bonding does not necessarily take place immediately upon exhaustion. It can take more time.

I don't know how much of your Lanaset dye has bonded to the fiber in the first couple of minutes. Some of it might bond very quickly. The 45-minute recipe probably includes an extra margin to be sure that all of the dye that's going to react has done so. When you want to be sure to get as much color yield as possible from a given amount of dye, it's probably a good idea to use the full time, but you might do just about as well with less time.

You'd have to experiment if you want to be sure. In order to tell how much of your dye has not only exhausted but also formed bonds, you have to do the full washing out process (whatever that means for a particular dye) on one sample, and compare the results to the unrinsed fiber in another sample. (I have not done this, myself.) You'd have to do this for each color, since the chemistry of a different dye, in the same group of dyes, can be surprisingly different, in some cases. Or, you can just be sure to use the full time when full color intensity really matters, and cut the time shorter when it doesn't, and always wonder. Certainty requires a lot of trouble!

-Paula