                  (1) Rita Udina  Paper & Books Conservation; C. Sant Pere, 24; Premià de Mar – 08330, SPAIN; info@ritaudina.com (2) South Florida Art Conservation; 500 Palm St. Ste 35, West Palm Beach, Florida 33401, USA; aem@sflac.net  Powdered microcellulose is commonly used in the paper conservation lab for filling small losses, concealing stains and treating other damages on paper. Its neutral pH, general chemical stability and low toxicity, makes powdered cellulose a very reliable and compatible material proved to be suitable for conservation purposes, like infilling and colour matching of the paper support. However, the ageing of this pure powdered cellulose, especially when modified by toasting to adjust its colour, is unknown. Obviously, this toasting gives room for some chemical changes, that’s why conservators should look for possible caveats of its use. To determine the possible limitations of the use of microcellulose powder in the long term, some rtificially induced degradation tests have been performed. The test results presented in this paper show that the changes occurred are not significant enough to prevent its use in paper conservation. !" Microcrystalline powdered cellulose; artificial accelerated ageing# infilling; light bleaching; paper conservation $%  Cellulose powder is being widely used in paper conservation to conceal stains, fill small losses or gaps in tears, diminish abrasions, and repair damages created by silverfish or tape [1][2][3]. Since micro cellulose is a very similar material to paper, the visual results obtained using it are very pleasant. In order to match its colour to the support in which it is going to be applied, it is common practice to have it toasted on a pan or hot plate. Different toasting times allow various degrees of browning of the powdered cellulose. Preparing the cellulose powder at different tones will allow the conservator to pick a colour as similar as possible to the surface of the paper that needs to be matched. Overall, cellulose is a very stable product; toasting it to give it a certain hue might seem quite a dramatic method regarding its durability, especially when it comes to guaranteeing the best quality and stability of the products applied in conservation treatments. This paper intends to look at the possible alteration of the cellulose after this toasting, the possible side effects and how to diminish or solve these issues, if at all necessary. 1