As mentioned in this post the developer is divided into two parts as a stock solution. Part B is the larger quantity of the two and suffers from settlement where the powder comes out of suspension and accumulates at the bottom of the bottle. Before use, you should shake the bottle well so that it goes back to a milky colour. It would seem that the larger the crystals in packet B the more drop out there will be. I have not yet found a method that stops this.