The present invention relates to a two-part cosmetic product that imparts a filling and/or swelling effect to hair, eyebrows or eyelashes, preferably a mascara. The invention uses an anhydrous base coat composition with a water absorbing ingredient being a salt of acrylic or polyacrylic acid and a CO2 releasing compound which is a carbonate or bicarbonate to expand or swell the film former of the top coat with the in situ generated CO2 when the water containing top coat is applied to the anhydrous base coat.