An alternative to adding gels and other impasto or building mediums to paint which work by imparting their own thicker bulk to a paint mix.
This medium actually chemically thickens the paint. It is a rheology modifier, that is, it changes the flow and viscosity of the paint, it will thicken the paint without losing any colour.
Some colours may show a reduction in sheen in the dried film which can be adjusted with a varnish once dry.