The brand of eye make-up remover I use comes in a clear plastic bottle. When new and unused, the liquid settles into two distinct layers, in a 50:50 proportion. I shake the bottle before I use it so the two halves are completely mixed. Despite this, with use, the proportion begins to vary. After I have used about a third of the bottle, the proportions are roughly two-thirds to one-third, with the upper layer becoming twice the depth of the lower. By the time half the bottle has been used up, there is a very thin bottom layer, with the majority of the liquid being in the upper layer. What is going on, and might it in any way alter the efficacy of the product?
Marian Smales, York, UK