portraits are especially useful to costume historians. Technique Johnson uses a number of techniques that taken together uniquely identify his studio during his early career. These include the presence of both wet-in-wet and discreet layering; calculated variations in brushwork and the use of high quality (and expensive) pigments that survived aging well. He "was masterful in bringing the unique characteristics of his pigments to the most dazzling effect. Johnson’s use of azurite blue is a primary example of how he utilized the character of each pigment to yield distinctive textures and eye-catching details." Johnson was consulted by Théodore de Mayerne on handling orpiment (a poisonous yellow pigment) and painted his portrait. In addition to describing his usage of orpiment to de Mayerne, Johnson also told Daniel King his technique for draperies. For linen draperies he used "white and oker broken with bone black". For blue draperies, he first laid in "all the background folds and shadows ... neatly and perfectly finished" with "indico ground in drying oiland mixt w[i]th smalt and white". When this had dried, he painted over it a glaze of ultramarine and "fair white". Exhibitions, sales and ownership of his work in important collections From the second half of the seventeenth century onwards, there were frequent art auctions in London and later in provincial cities. Johnson's work was regularly sold at these auctions – for example lot 150 at a sale of paintings at Exeter Exchange in the Strand, 3 April 1690. Karen Hearn, Honorary Professor at UCL, curated a display of Johnson's work which was held at the National Portrait Gallery from April to September 2015. In July, 2016, the first large scale exhibition devoted solely to his work was held at the Weiss Gallery in London. His work can be found in the National Gallery, the Tate Gallery, The National Portrait Gallery, Royal Collection, the Scottish National Portrait Gallery, the Dulwich Picture Gallery, many UK provincial galleries and in private collections in stately homes in Britain. Outside the UK, his work can be found in the Huntington Library, Art Collections and Botanical Gardens, the Museum Catharijneconvent in Utrecht and the Yale Center for British Art. His Portrait of a Lady was part of the exhibition of Tudor and Stuart Fashion at the Queen's Gallery. Johnson's name is attached to the Johnson portrait of William Shakespeare in the Folger Shakespeare Library. This was painted around 1610