Varnish refers to a protective coating applied to a finished artwork to preserve and safeguard it from environmental factors such as dust, ultraviolet light, and moisture. According to the provided articles (Source ID: various), varnishes can be customized to meet specific needs, including protection from harsh chemicals, high temperatures, and moisture. Golden Artist Colors offers various varnishes, including removable and non-removable options, with different finishes like gloss, satin, and matte (Source ID: product_content-114). The application of varnish requires careful consideration of factors such as surface preparation, brush selection, and technique to ensure a successful outcome (Source ID: various). Golden Artist Colors provides guidance on varnishing, including tips and best practices for artists to achieve the desired appearance and protection for their work.