Paraloid B-72 is an acrylic resin (ethyl-methacrylate copolymer) used as a consolidant, soft varnish or strong adhesive when mixed with a solvent (e.g. acetone, toluene, isopropyl alcohol or ethanol). It comes in solid pellets which are then dissolved in a solution (which can take many hours and often overnight).
Paraloid B-72 is a conservation-grade material that is widely used due to its transparent, flexible and reversible properties. It is non-yellowing over time. It essentially 'plasticises' a rock or fossil as it penetrates.
Solutions can be mixed to the desired consistency. A 50-80% wt/vol solution or a higher concentration creates a strong glue, which fills pores and gaps. 3-10% solutions are used as consolidants of friable, crumbly or soft and fragile matrix. An 8-10% solution can also be used as a reversible varnish for fossils, providing a soft gloss finish.
100g will make 1 litre of 10% wt/vol solution or 2 litres of 5% wt/vl solution. A little goes a long way!