Abstract: Multilayer anti-microbial materials formed to produce an interference colour, and thus an indictor of anti-microbial effect, are provided. The materials include a partly reflective base layer and a partly reflective, partly transmissive top layer balanced to produce an interference colour. The top layer is formed from an anti-microbial metal with atomic disorder. Dissolution or a change in composition of the top layer on contacting an alcohol or electrolyte causes a change in optical path length so as to produce a change in the interference colour of the material. Multilayer, laminated wound dressings are also provided. The dressing includes a first and second layer, and preferably a third layer. The first and third layers are formed of perforated, non-adherent materials and most preferably carry an anti-microbial coating as above. The second layer is sandwiched between the first and third layers and is formed of an absorbent material. At least one of the layers is formed from a plastic material.

Abstract: Production of an anti-microbial effect in an alcohol or water based electrolyte is achieved by preparing silver materials that form complex ions other than Ag.sup.+, Ag.sup.2+, or Ag.sup.3+, and which produce an anti-microbial effect that is greater than that produced by an equivalent amount of silver as Ag.sup.+. Exemplary complex silver ions produced include Ag(CN).sub.2.sup.-, AgCN(.sub.aq)(ion pair), Ag(NH.sub.3).sub.2.sup.+, AgCl.sub.2.sup.-, Ag(OH).sub.2.sup.-, Ag.sub.2 (OH).sub.3.sup.-, Ag.sub.3 (OH).sub.4.sup.-, and Ag(S.sub.2 O.sub.3).sub.2.sup.3-. The silver materials may be prepared as powders or as solutions or suspensions containing the complex silver ions. The silver materials might also be prepared as coatings, foils, powders, or fine grain or nanocrystalline powders, which are formed with atomic disorder to provide sustained release of the complex silver ions.