Forty years ago in a xxth-century church in Torino, a small fire partially burned some of the decorative external boards of the sound-box of the organ. The focus of this present work was to find a treatment able to consolidate partially burnt wood in dry conditions, in which the external charred layer would be lost if not well preserved because of its incoherence. The product had to be applied onsite on an architectural structure intended to be reused again (and not simply exhibited). This circumstance is rarely encountered in the conservation of wooden Cultural Heritage. The efficacy of treatments was evaluated on the basis of a suitable and original experimental methodology, which took into account both the immediate and long-term behaviour of the various tested products. Although the opportunity to carry out this work came from a real case, both the selected product and the set up evaluation methodology have a general validity and they can be effectively used in other similar situations in which a slight antipowdering effect is required for treatment.