The sponge should first be thoroughly wet in clean water and wrung out dry before the oil color is applied by it.
The tools needed for oil color are the flat brush, combs, fitch tool or fresco-liner, sash tool and a piped bristle overgrainer.
The oil color must be very thin and fluid, because a tougher one will take hold of the fibres of the paper and tear them off.
oil color is sometimes used to pencil in the hearts, as it will not lift the stippling, no matter how much it is blended.
It should be done with the oil color used in graining it in oil for either oil or distemper work.
When the oil color is dry, the work may be shaded or overgrained in either oil or water color.
When this is dry, rub in the oil color and wipe out the hearts with the rag in the same way as for oak and ash.
The bristle overgrainer of the fitch tool is used to put in the finer grains, or this may be done when the oil color is dry.
All the above applies to oil color marbling only as work done in distemper is never varnished.
You can tone down any oil color, however, by stippling it with a stipple brush dipped in a pan of dry color, or plaster Paris.