Assorted Blue Chefs Detectable Fabric Dressings / Plasters (Box of 100)The A Care Washproof Blue Detectable plaster is recommended when handling food and where contamination is a risk. Visually Detectable Blue is the one colour that does not occur naturally in food. Metal Detectable. A metal strip is positioned behind the lint pad becoming the key component for detetction. Washproof. Withstands routine handwashing and prevents cross contamination. Plaster sizes: Small square patch x 10. X Wide x 10. Knuckle x 5.