Description of a Process
used by the Prussians to protect
Steel Gun Barrels against Corrosion
The introduction of steel Krupp breech loaders into Prussian service posed the problem for the Prussians of protecting the steel barrels against corrosion. The method adopted was Brunieren, in which the barrel would be chemically treated such that it was protected against corrosion and as a result of which it would end up with a bronze colour. This finish could then be maintained over a longer period. The officially-recommended method of Brunieren was described in the "Leitfaden zur Unterricht über die gezogenen Geschütze 1861". The method described below is not the official one, it is one that was found to be successful during experiments in Berlin during the 1860s.
Preparation of the Beitze (The Beitze is the chemical mixture which protects the steel)
To one part of iron chloride are added four parts (by weight) of iron oxide (Vitriol). For each loth of this mixture, add six and two-thirds loth of distilled water. (`Note: there were thirty two loth to one Prussian pound. In 1870 a Prussian pound weighed 500 grammes, one loth weighed around 10.65 grammes.)
Initial Tasks
All grease is to be removed from the surface of the barrel by sanding. Any rust marks or remains of previous treatments need not be removed. After this the barrel should be coated with limewash or wet chalk, when this has dried it should be wiped clean with linen rags. From here on the barrel should not be touched with bare hands, as this will cause stains which are very difficult to remove.
The support on which the barrel is resting should be as narrow as possible.
The process should be carried out in an area where the barrel is protected against dust and rain.
Brunieren of the Barrel
The brunieren itself takes five full days. The beize is painted on in a uniform thickness with a flat brush, and after 24 hours the covering of red rust which has formed is removed with a wire brush. The barrel is then wiped down with hot water and linen rags, with the darker areas receiving the most attention so that a uniform colour is obtained. The barrel is then dried using löschpapier (blotting paper) and linen rags. The second coating of the beize is then applied immediately, and the whole process is carried out five times in all. During the final washing down with hot water particular attention is paid to achieving a uniform colour. Finally the barrel is painted with a thin layer of linseed oil, this is then rubbed in with the hand until it is almost dry. The colour will darken somewhat subsequently.
Maintaining the treated Barrel
In order to maintain the treated barrel in the best condition it is not be wiped using dry rags, any dust or dirt should be washed off. The barrel should then be dried.
From time to time the barrel should be treated with linseed oil in the manner described above.
Anyone who wishes to recreate this process, for example a reenactor, please bear in mind that there are strong chemicals involved, and every precaution must be taken.
Website "The Franco-Prussian War 1870-71" © Martin Tomczak 2004