They are rich colors and can be used for all over coverage similar to an opaque underglaze.  Colors may be mixed together to create unique colors.  Use on greenware, then bisque prior to applying a clear glaze.  Or use on bisque with a covering glaze applied prior to firing.   Velvets tolerate a wide firing range, and can be used on most temperatures and clay bodies.  Some colors may fade at high temperatures (cone 7 and up).  When used without a glaze cover, Velvets should not be used on food or drink containers.   All are Lead free.  All are non-toxic in liquid form.  Have been tested and approved for dinnerware when covered by LG10 clear glaze.   Glazes with Zinc can cause discoloration of underglazes.  Use of Zinc-free covering glazes are recommended.
They are rich colors and can be used for all over coverage similar to an opaque underglaze.  Colors may be mixed together to create unique colors.  Use on greenware, then bisque prior to applying a clear glaze.  Or use on bisque with a covering glaze applied prior to firing.  
Velvets tolerate a wide firing range, and can be used on most temperatures and clay bodies.  Some colors may fade at high temperatures (cone 7 and up).  When used without a glaze cover, Velvets should not be used on food or drink containers.   All are Lead free.  All are non-toxic in liquid form.  Have been tested and approved for dinnerware when covered by LG10 clear glaze.  
Glazes with Zinc can cause discoloration of underglazes.  Use of Zinc-free covering glazes are recommended.
V) Velvet Underglaze : Underglazes
V) Velvet Underglaze : Underglazes
Amaco Velvet Underglaze - 2 Ounce Jar - V-370 Velour Black
Amaco Glaze Packs & Sets for Classrooms
Red Brown Velvet Underglaze is a warm cocoa color that is reddish at cone 05. The color darkens at cone 05, and becomes chocolatey at cone 10. A clear
Amaco V-313 Red Brown Velvet Underglaze (2 oz.)
Amaco Velvet Underglaze Set - 2oz Bottles (12 Colors)
Amaco Velvet Underglaze 2 oz. White
Review Amaco Velvet Underglaze Set #2 (12x 59ml) on CCG
Amaco F Series Low Fire Pottery Glazes (6 Pints)
AMACO Velvet Underglaze Set fire true to and have the soft look of velour when unglazed. Glazes can be fired to cone 05/06 for detailed design work or
AMACO Velvet Semi-Translucent Underglaze Set 2, Assorted Color, Set of 12
V-345 Light Green (2 oz) Amaco Velvet Under-Glaze Amaco Velvet UnderGlazes are semi-translucent. Note: Choose from the LUG underglazes for more opaque
V-345 LIGHT GREEN (2 OZ) Amaco Velvet Under-Glaze
V-386 Electric Blue (2 oz) Amaco Velvet Under-Glaze