Retarder is an additive used to increase the open (drying) time of acrylic paints. Useful for wet in wet techniques and reducing skinning on the palette.
Golden believe that artists have the right to know what chemicals they are working with, and so have developed their own Health & Safety labelling system. You should follow basic precautions when using any Golden Products. Each label gives pigment identification information as well as general guidelines for safe use, and on Material Safety Data Sheets (MSDS) which list hazards of product components without incorporating the use assumptions of toxicological risk assessment. Golden's label advice for using chemical products safely, while conservative, emphasizes the need to err on the side of caution when using art materials. It's a lot of information to fit onto a label, Golden believe it's the best service they can offer. More information about Golden Health & Safety Labelling