Molten shellac is twisted through a huge strip of cloth and poured onto trays where it cools to form into buttons, these are either sold as is for making brown button polish, or used as the raw material for making high purity flake shellac.
Shellac is a fantastic finish, it is non-toxic, easy to apply, repairable, adjustable for depth of colour, dries in minutes, can be applied over oil.
It's not just for French polishing either. You can apply it with a brush or polishing mop, spray it or just rub it on with a lint free cloth. A few layers of shellac over a well dried oil finish will seal the surface and allow varnishes to be used over the top, it can also be used as a sanding sealer.
Mixed with methylated spirits in the same way as flake shellac, buttons take a little longer to dissolve but produce a wonderfully rich golden brown finish that is particularly favoured by restorers of antique furniture. You may find some sediment at the bottom of the container after dissolving - this is completely normal - just carefully pour off the transparent liquid at the top into a clean container.
Shellac is usually mixed in 'pound cuts' - i.e. a two pound cut = 2lb of shellac in a gallon of meths or alcohol. That's far more than any of us are likely to need, but if you want to make smaller quantities it's much easier to subdivide if you go metric.
1 gallon = 4.54 litres
1lb = 453g
So 10g of shellac in 100ml of meths is a 1lb cut, 20g in 100ml is a 2lb cut and so on.