Retarder Medium

Retarder Medium

Retarder Medium is an additive to extend the ‘open’ or drying time of Jo Sonja Matte Flow Acrylic or Mediums. It may be used as both a painting medium and for various techniques such as antiquing.



  • To use Retarder as a painting medium, lightly moisten the brush with Retarder before picking up paint.
  • To further extend working or ‘open’ time, Retarder may also be applied directly to a prepared surface.  A mop brush may be used to ensure an even application.
  • Mix Retarder directly into palette colours beginning with a ratio of approximately 1 part Retarder to 3 parts of colour to delay the drying time of the paint.  Adjust ratio as required for technique.  The more Retarder that is added, the more transparent the colour becomes.



  • A barrier coat of Clear Glaze Medium is recommended before antiquing, then thin paint with Retarder using a ratio determined by the strength of colour desired.  Begin with 1 part paint to 1 part Retarder.
  • Apply over painted surfaces and then wipe off to produce an aged effect.  For additional open time, apply a light coat of Retarder directly to the surface.  Use a small amount of Retarder on cloth to remove excess.
  • Allow 48 hours drying time before varnishing.  An extended dry and cure time should be allowed and varies due to humidity and climatic conditions or if an excessive amount of Retarder has been used.  A hair dryer may be used to speed surface drying.
  • A coat of Clear Glaze Medium is recommended prior to application of varnish.


Approximate coverage: 1 ml = 251 sq cm / 1oz = 8 sq ft.

Safe to dry with a hair dryer.

Water based, can be cleaned up with mild soap and cool water.

Conforms to ASTM D 4236 and is Non Toxic.