Royal & Langnickel's 12 piece gouache tube set is an excellent high quality assortment of 21ml paints and is a perfect foundation for all your painting needs. 12 Tubes of high quality student grade paint. Royal & Langnickel gouache is an opaque paint that produces smooth washes with good coverage. Wet on Wet Technique - Use a silk sponge to wet the paper. Colours will spread easily and will appear fuzzy. Bold Colour Technique - Use the colours full strength for bold opaque coverage or miss them together for more colour tints.