Another calculator for proportions, but a little bit tricky. It is about glue solution. You have dry glue (bone glue or leather glue) and water and you need to make a glue solution of required strength. The tricky part is that glue, no matter how dry it is, still contains water, The water concentration in dry glue is about 12-15%, thus glue has concentration only about 88-85%. This should be taken into consideration when creating a solution. The solution will contain added water plus water already contained in dry glue. So, the calculatro below can save you some time by solving several proportions at once and showing you how much dry glue and water are needed to get required mass of solution with required strength (concentration).