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Jo Sonjas

Crackle| Medium - 60ml bottle dual set

Crackle| Medium - 60ml bottle dual set

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Chroma's Jo Sonja Crackle Medium is a transparent medium designed to create fine, cracked patterns in a single-step process, simulating the effects of ageing. It is specifically formulated for use with Chroma’s Jo Sonja Artists’ & Background Colours. Testing your technique on a small scale before starting a full project is recommended.


  • Application: Apply a thin coat for fine cracks, a moderate coat for medium cracks, and a thick coat for large cracks.
  • Background Crackle Preparation: Seal the surface and apply a basecoat. For one-step preparation, mix All Purpose Sealer with the basecoat colour, starting with a ratio of up to 1:1 for the first coat only. Allow to air dry and lightly sand before applying additional coats without the sealer.
  • Crackle Medium Application: Once the final basecoat is dry to the touch, apply Crackle Medium in a small area at a time using a criss-cross motion with a suitable brush. Blend out brushstrokes slightly as you apply. The crackle pattern will follow the direction of the brushstrokes. Avoid reworking areas that have begun to dry as this may cause the medium to lift. The medium will dry clear and level out slightly.

Important Notes:

  • Drying: Allow to air dry undisturbed. Do not use a hairdryer between coats; warm air can cure the paint and inhibit the crackling effect. The base colour will show through the crackle pattern.
  • Post-Application: Once the crackled surface is completely dry, gently sand with #400 to #600 grit sandpaper until the desired smoothness is achieved. Wipe away dust; any remaining dust in the cracks will be incorporated during antiquing or glazing.
  • Surface Finish: The Crackle Medium will leave the surface slick; light sanding can reduce this slickness.
  • Antiquing: To highlight the crackle pattern, apply antiquing over the surface. If painting over the crackled background, apply 1-2 coats of Clear Glaze Medium as a barrier coat. Thin a contrasting colour with Retarder Medium and work into the cracks. Wipe away excess with a moist soft cloth.


  • Crackle Medium can also be applied over completed paintings or prints to produce fine crazing for an aged effect. Apply a coat of Clear Glaze Medium before the crackle application. Light sanding before antiquing is advised.

Approximate Coverage: 1 ml = 62 sq cm / 1 oz = 2 sq ft.

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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.