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Jo Sonjas

Retarder and Antiquing | Medium - 237ml Bottles

Retarder and Antiquing | Medium - 237ml Bottles

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Retarder Medium is an additive that extends the ‘open’ or drying time of Jo Sonja Matte Flow Acrylic and Mediums. It serves as both a painting medium and a tool for various techniques such as antiquing.


  • As a Painting Medium: Lightly moisten the brush with Retarder before picking up paint. This will extend the working or ‘open’ time during application.
  • For Extended Working Time: Apply Retarder directly to a prepared surface using a mop brush to ensure even coverage.
  • Mixing with Paint: Begin mixing Retarder into palette colours with a starting ratio of approximately 1 part Retarder to 3 parts paint. Adjust the ratio as needed for your technique. Adding more Retarder will increase the transparency of the colour.


  • Preparation: Apply a barrier coat of Clear Glaze Medium before starting the antiquing process.
  • Application: Thin the paint with Retarder, starting with a ratio of 1 part paint to 1 part Retarder. Apply over painted surfaces and wipe off to produce an aged effect. For additional open time, apply a light coat of Retarder directly to the surface.
  • Cleanup: Use a small amount of Retarder on a cloth to remove any excess paint.

Drying and Curing:

  • Allow 48 hours of drying time before varnishing. Extended drying and curing time may be necessary depending on humidity and climate conditions or if an excessive amount of Retarder is used. A hairdryer can be used to speed up surface drying.

Before Varnishing:

  • Applying a coat of Clear Glaze Medium before varnishing is recommended to ensure the best finish.

Coverage and Safety:

  • Coverage: Approximately 1 ml covers 251 sq cm, 1 oz covers about 8 sq ft.
  • Cleanup and Safety: The product is water-based, non-toxic, conforms to ASTM D 4236, and can be cleaned up with mild soap and cool water. Safe to dry with a hairdryer.
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About Jo Sonjas Paints

The Paint: Jo Sonja's Artists Colours

Discover the vibrant potential of Jo Sonja’s Artists Colours, specially formulated flow formula acrylics that emulate traditional gouache. Crafted from the finest quality, pure pigments, these colours provide artists with exceptional coverage and a velvety matte finish. Ideal for intricate layering, the quick-drying nature allows for overpainting without damaging earlier layers, facilitating seamless corrections and enhancements to your artwork.

Unlike typical craft paints, Jo Sonja's offers a professional range designed for the discerning artist. Each colour is two to three times more concentrated, ensuring that your creations will pop with permanent, brilliant hues. Simplified use comes standard, as these paints are designed for immediate application without the need for complex instructions. Whether you’re a hobbyist or a professional, Jo Sonja’s Artists Colours are engineered to elevate your artistic vision to new heights.


Jo Sonja acrlic paints, About the paints


Jo Sonja's® Artist Colours & Mediums

Founded in 1985 by Jim Cobb, Director of Chroma, and celebrated folk artist Jo Sonja Jansen, Jo Sonja's Decorative Painting System is a testament to innovation and artistic tradition. The collaboration aimed to fulfil the sophisticated demands of serious artists, combining Chroma's cutting-edge technology with versatile, long-lasting products. The system offers unparalleled flexibility, enabling artists to master historical techniques and pioneer new ones, thus securing a robust foothold in the decorative painting market.

Artists around the globe have come to recognize and value the brand's exceptional quality. Jo Sonja’s continues to influence the decorative arts significantly, with Chroma's commitment to innovation and excellence ensuring its ongoing leadership and presence in the market.


The Decorative Painting System

With the range of paints, also comes a range of mediums to allow unlimited techniques.  Acrylic mediums are invaluable if you wish to change the paint consistency or alter drying times.  Chroma has discovered ways of allowing the same set of colours to be applied on a variety of surfaces such as wood, metal, glass and textiles.  The same colours (with the use of the mediums) can be stencilled, stamped, crackled or used in a host of elaborate faux finishes.  By experimenting with the mediums, there are endless possibilities that can be achieved.  Technique information sheets, designed to inspire your imagination, can be found on this website.   Chroma continues its research and development of new products. 

 The range of jo sonjas products

ASTM Standards and Jo Sonja's Artist Colours

Jo Sonja's Artist Colours are crafted using the highest quality pure pigments, adhering to rigorous ASTM (American Society for Testing Materials) standards. This independent body ensures reliable classification for pigment lightfastness and health labelling standards. Each colour in our range boasts an ASTM rating, affirming its resistance to fading and guaranteeing that the hues will remain vibrant and true for generations.

Our ongoing commitment to quality is reflected in continual testing and stringent quality controls, allowing artists to trust implicitly in the enduring brilliance and performance of our paints.


Jo Sonja's Paint Quality and Standards

ASTM Ratings: Ensuring Colour Longevity

ASTM 1 – Excellent Lightfastness: Highest rating, indicating superior resistance to fading.
ASTM 2 – Very Good Lightfastness: Very reliable in maintaining colour integrity over time.

    Note: All Jo Sonja’s paints are rigorously tested and carry either an ASTM 1 or 2 rating, ensuring top-tier durability and fade-resistance for your artwork.

    Archival Quality:

    Archival Standards: Jo Sonja’s paints and mediums are not only lightfast but also archival and lignin-free, making them an ideal choice for artworks intended for long-term preservation.

      By using Jo Sonja’s paints, artists ensure their creations remain as vivid and impactful as the day they were painted, backed by our commitment to quality and enduring performance.