Need to touch up painted or discoloured grout The Ronseal One Coat Grout Pen quickly and easily transforms the surface giving a durable and waterproof finish in one coat. So now there's no need to re-grout. Colour Brilliant White. Available in Two Sizes (ml). Areas of use Interior tiles. Approx. number of coats 1. Application Pen. Drying time Approx. 24 hours. Protection level Medium. This Ronseal RSLGPBWH15 is a 15ml Pen with re-sealable lid