Improvements in Fire and Sound Proof Plastering.
Year: 1889

page_text: COMPLETE SPECIFICATION.
Improvements in Fire and Sound Proof Plastering.
I WILHELM DOEHRING of 144 Linienstrasse Berlin, in the Empire of Germany,
Royal Architect and Engineer, do hereby declare the nature of this invention and in
what manner the same is to be performed to be particularly described and ascertained
in and by the following statement :-
•
The object of the improvements in wall and ceiling plastering bereinafter described
is to construct a fire proof and sound subduing as well as a porous and light
plastering upon the ordinary wall or ceiling construction or framing, whether the
latter consist of separate boards or laths, with intervals or of continuous boarding or
of other wooden, brick, cane or metal netting or wire construction.
The object of the improvements consists more especially in first covering the surface
with an easily hardening fire proof layer, principally a mortar which is mixed with
soluble glass and before its hardening, spreading over it a layer of coarse sand or
gravel or other lumpish material which adheres thereto and is qualified in consequence
of its projecting and rough surfaces to hold firmly the porous finishing plastering
and also is proof against fire. This finishing plastering consists principally of a porous
material which is made fire proof by impregnation, so that by the composition of these
three layers, a fire proof, sound subduing very light and porous covering is made
which when heated as for instance by fire does not peel off nor crack, and is a bad
conductor of heat so that walls and ceilings which are plastered with this material are
cool in summer and warm in winter.
This method of plastering is performed, according to this invention as follows:
Boards, bands, laths etc. of wood metal or metal netting are fixed underneath the
beans or upon framework and are provided in the first instance with a thin ground
plastering.
The same is made of any convenient mineral, salt or oxide adapted to combine with
silicic acid to form a silicate for instance oxide of zinc the said salt or oxide being
stirred up into paste in a solution of soluble glass with silicic acid and carbonate of
lime.
The said mineral salt or oxyde is pulverized and first mixed with the silicic acid
about 9 parts, but this quantity varies according to the quality of the other ingre-
dients, then the solution of glass is added and by a proper stirring of the latter it is
made into a homogenous paste-like mortar convenient proportions being zinc oxide
This imortar is layed in proper
100 parts, water glass 300 parts and lime 600 parts.
thickness on the wall or ceiling covering or the like either before or after its attach-
ment to the beams or wall framing and sticks firmly without further trouble.
The strength or thickness of this first layer depends upon the coarseness of the
gravel or sand which is now to he added.
Upon this first foundation plaster is added before the former hardens, a clean coarse
sand or gravel (for this sand or gravel layer can be substituted any convenient coarse
or rough substance) which is retained by or in the surface of the first foundation
plastering layer and firmly set therein during the glass like hardening of the former.
According to the amount or degree of fire proof quality required the first plaster
layer can be spread more or less thick and the first or second plaster layer may be
repeated.
When these first two layers are set, then follows the third or main plaster layer of
a thickness of several centimetres. This latter is made of a mortar mixture the
ingredients of which are gypsum and cellulose in equal proportions if the gypsum is
of good quality or gypsum and cellulose.
In order to deprive the cellulose of its inflammable natnre as well as to ensure a
quick hardening of this mortar mixture the cellulose is steeped in or impregnated
with sulphuric acid or ammonia alum. However it is not absolutely necessary that

page_text: the cellulose be impregnated before hand. In case of the non impregnation the
plastering layer is put on thicker when more fire proof, subduing of sound and bad
conduction of beat is required.
The proportion of addition of the cellulose to the gypsum varies according to the
desired weight and purpose of the mixture of mortar whilst the concentration or
strength of the impregnating solution for enhancing the fire proof qualities of the
mortar depends upon the desired rapidity of hardening of the mortar to which
qualification the impregnating solution contributes to a considerable extent.
The plastering is now complete and receives, because it is porous only another thin
mortar layer made up of any known plaster mixture which is weather and water proof.
This plastering thus compounded is painted or papered over according to requirements
on the interior of buildings the same as other plasterings. When used outside how-
ever it is covered with one or more coats of paint.
If the plastering is to afford the highest possible proof against fire the mortar
mixture of the first foundation plastering layer mentioned above which is placed direct
upon wood or construction is varied so as to make a completely fire proof mortar by
leaving out the cellulose and this plastering or mortar is made as follows
1. Pulverized coarse carbonate of lime such as chalk chalk stone powder, marble
powder or the like is taken in the proportion of 350 parts.
2. Silicic acid sufficient added to give firmness say 100 paris.
3. Metallic oxide 50 parts.
4. Waterglass 500 parts
to which mixture is then added sand, or instead of sand brick earth, burned brick or
argillaceous earth up to the desired consistency.
The proportion of the mixture of these substances depends upon the nature of the
separate parts used and their nature of reabsorbtion. According to whether more or
less proof against fire is to be attained the addition of more or less earth is balanced
by the addition of more or less silicic acid i.e. clean sand or gravel.
By using these improved mortars or plasterings according to the method before
described the purpose is arrived at of producing a very light, porous, sound subduing
ceiling or wall plastering which does not conduct heat so that the same not only
prevents the penetration of fire from one storey to another but through the walls or
partitions. The improved plastering also has the property of not cracking when
heated or when brought into conjunction with water when in a heated state. This
plaster subdues the sound at the same time in a manner not attained heretofore and
can be used everywhere on wood iron, stone, glass, and brickwork and not only as
ordinary wall plastering but also for the formation of fire proof plaster floors upon
any optional foundation.
Wooden buildings or separate parts of wooden buildings are by the use of this
plastering rendered proof against fire in an eminent degree and the effect is arrived
at in the following manner.
The first foundation plastering layer has here a double purpose. On the one hand
it produces a fire proof connection between the bed of the laths and the second
plastering layer and secondly it holds firmly the gravel or sand layer which is to be
added.
The gravel or sand layer which is named here the second plastering layer should be
adapted to render very lasting the third very porous plastering layer by the adhesion
between the separate grains of gravel or sand and fo hold the same firmly in any
thickness even up to 10 centimetres thickness and more even against great vibration.
The third plastering layer to be put on in the thickness of several centimetres has
the purpose to form the proper sound subduing light and porous covering, which does
not crack through fire and which the proportionately large addition of cellulose does
not only make porous and light but also renders non conductive of heat.
The porous nature and the elasticity of this porous plaster layer has further its special
purpose to prevent any hurtful influence from vibration or movement of the walls or
ceilings which might happen and to prevent cracks as well as to give the plastering
itself a firm connection when under the continued influence of fire.

page_text: The fourth and last thin plastering layer has only the purpose to form a suitable
water and weather proof covering for the plastering and painting. The boardings or
the laths for ceilings and walls may consist of optional cross section; however it is
suitably composed of perfectly flat three or four edged bands, because with this
arrangement no inconvenience is experienced from the bending of the wood work.
The bands are fastened to the beams by direct nailing on in the usual manner or
are kept by wires.
The second kind of the extra fire proof mortar without addition of cellulose above
described is employed for the production of plastering either in connection with the
above named first method of plastering or independently by itself where it does not
matter whether the extra fire proof plastering layer is used beneath or above the
plastering made according to the first method.
Having now particularly described and ascertained the nature of my said invention
and in what manner the same is to be performed, I declare that what I claim is,
1. As a plastering material, the combination of gypsum and cellulose in proportions
substantially as set forth for the purpose herein specified.
2. As a plastering material the combination of gypsum and cellulose previously
impregnated as described in proportions substantially as set forth for the purpose
specified.
3. A plastering consisting of an under layer composed of soluble glass, lime and
silicic acid, a layer of gravel or coarse sand or rough material thereon as set forth
and an over layer composed of gypsum and cellulose impregnated or not impregnated
as described in proportions as set forth.
4. A fire proof plastering consisting of silicic acid a mineral salt or oxide adapted
to combine therewith to form a silicate soluble glass and burned brick or brick earth
or the like as set forth in proportions substantially as specified.
Swed
COISA day or Buy 100.
HERBERT & Co.,
18, Buckingham Street, Strand, London, W.C., Agents to Applicant.