Every day I take 10g of hydrolysed collagen dissolved in about 200ml of water.
First I put the cup of water on my digital scale (which measures in 0.1g increments) then I add exactly 10g of collagen and stir it with a spoon until it dissolves.
As the collagen dissolves, the total weight always gradually decreases by about 1.5g - 2g in total. If the total weight of the cup, spoon and water is 300g, when I add the collagen, it becomes 310g, then as it dissolves over the next 15 seconds it decreases to about 308g. All I've done is stir it.
I can't see how this is due to evaporation since I can leave the pure water on the scale for 5 minutes beforehand and the weight doesn't change; but as soon as I stir the collagen in it always decreases.