(9) At the requisition of the Belgian Minister of Public Works, Boudin and Donny, professors at the Ghent University, have conducted a series of experiments and investigations in connection with rendering wood uninflammable. The following resume embodies the conclusions at which they arrived.
Although wood cannot practically be rendered so fireproof as not to be destroyed by heat, it is very possible to deprive it to a considerable extent of the property of catching and communicating fire; and to this end it is sufficient to coat the wood with a suitable composition. It is not, however, sufficient that this composition possesses in a high degree the property of rendering wood uninflammable. The treatment must not involve an expense out of proportion with the purpose to which, the wood is applied; nor the process be such as to delay the rapid execution of works; nor the substance employed be liable toattack any metal parts which it may be necessary to use with the wood. The process should be of easy application, with a brush, for instance, the only manner in which it can be applied to existing structures. The wood thus coated should present a neat and tidy appearance, and should also be capable of receiving a coat of ordinary paint over the fireproofing composition; nor should one or the other coat be subject to alteration after a moderate lapse of time.
If, instead of coating, injection be employed, certain substances, notably chloride of calcium, should be rigorously excluded, because they would keep the wood constantly damp. The injection method is easily applied to small articles by simple immersion; and it is preferable that the composition or solution be hot, if not boiling. The possible diminution of strength due to all injection processes should also be taken into account, although the results of experiments are not conclusive on this point.
It follows from the above considerations that wood cannot be rendered incombustible, or more strictly speaking non-alterable by heat; but its non-inflaramability may, to a considerable extent, be ensured, so as to preserve buildings from a limited and temporary fire, at any rate until assistance arrives. It is, however, hopeless to expect a building encumbered with inflammable substances to pass through such a test uninjured.
The methods of preserving wood against fire are of two kinds: the injection of saline solutions, and the application of a paint or coating. The former appears but little practical; and indeed, short of proof to the contrary, it must be considered dangerous in the case of wood of large dimensions. Thh system is, however, applicable to small pieces of wood. Of all the substances recommended, a concentrated solution of phosphate of ammonia is undoubtedly the best, the use of this substance, notwithstanding its high price, possessing such great advantages that it should be employed in all cases where expense is no object. In the majority of cases, however, coating with a brush is the only practical solution of the question, and the substances most to be recommended for use in this manner are cyanide of potassium and asbestos paint.
(10) B. Hoff, professor of chemistry at the state college in Jaroslaw in Galicia, has produced in a cheap and easy manner a wood not only uninflammable but even incombustible. Following are the excellent qualities of this wood: Incombustibility at high degrees of heat (temperature when glass melts), whereby it neither burns with a flame- nor brightly glows, generates no suffocating gases or smoke, and gives out but little heat; a glow on the surface in the open air, as well as in a strong current, without burning or igniting thereby, but extinguishing momentarily. When exposed to great heat for a length of time there remain no ashes, but a compact coal which does not burn. At the same degree of heat zinc sheets melt in seven seconds; slate breaks into pieces, tiles become glazed, and felt for roofs burns with a bright flame. Besides this the last-mentioned roofing materials oner no protection whatever in case of fire breaking out from the inside, because they are fastened upon boards. The chemicals necessary for the production of the incombustible wood consist of the cheapest refuse of industrial establishments. The process of manufacturing is simple and cheap, and may be applied to all dimensions.
Shingles made from it have a pleasing appearance, resemble tiles, are cheaper and safer against fire than felt, zinc sheets, etc, and, since the process preserves the wood, last 25-30 years. (Gewerbe Zeit.) (11) The following treatment of wood is alleged to render it incombustible without any alteration in appearance. Intense heat chars the surface, slowly and without flame, but does not penetrate to any extent, and leaves the fibre intact, whereby in case of fire the firemen would have no occasion to fear that the materials on which they tread would give way beneath them, if this operation had been undergone by the wood composing the staircases, floor, etc. The chemical compound said to produce the result is: - Sulphate of zinc, 55 lb.; potash, 22 lb.; alum, 44 lb.; oxide of manganese, 22 lb.; sulphuric acid of 60° Tw., 22 lb.; water, 54 lb. All the solids are to be poured into an iron boiler containing the water at a temperature of 113° F. As soon as the substances are dissolved, the sulphuric acid to be poured in little by little, until all the substances are completely saturated.
For the preparation of the wood it should be placed in a suitable apparatus, and arranged in various sizes (according to the purposes for which it is intended) on iron gratings, care being taken that there is a space of about 1/2 in. between every two pieces of wood. The chemical compound is then pumped into the apparatus, and as soon as the vacant spaces are filled up, it is coiled for 3 hours. The wood is then taken out and laid on a wooden grating in the open air, after which it is fit for use.