Is it true that synthetic brushes are only best for oil- or crème-based formulations?
Most makeup brush companies only offer synthetic fibres in brushes intended for the application of emollient type formulas.
Up until lately, the most available synthetic fibres for makeup brushes has been nylon and taklon, and both of those are mainly smooth and more rigid fibres. Emollients apply more easily from a brush that has a fibre bundle that is firm and smooth, and nylon was the choice for some brushes [e.g. foundation brushes].
Those same companies avoided using the nylon in their brushes intended for powder application, because the smoother, stiffer nylon just didn't perform well in a brush bundle that was supposed to be soft and gentle.
But Artis® brushes exclusively make use of advanced fibres [CosmeFibre] which are available in many different shapes and textures, and this allows us to make any style of brush that is currently made out of animal hairs.