For sealing the surface of exterior brick or plaster/stucco/pargetting before painting. Black or very dark grey material, so hard it almost seems like a glaze fired on to the surface. Almost impossible to remove except mechanically with colateral damage. Cannot try heat as underlying surface is thin and unknown water content so may crack or steam burst apart. Proprietary name or generic name for the material or process? Some sort of stove-enamel?
On 24 Jan 2015, N_Cook grunted:
The ground floor floorboards of my Edwardian house are set on brick piers, between which the builders floated some form of bitumenous material over a thin of rubble for damp-roofing purposes, forming a flat, black, shiny layer. I wonder if that's a clue to your coating? Worth trying out a petroleum-based solvent and wire brush?
+1 Raw bitumen is very shiny and brittle.
Perhaps over time it seeps in and incorporates itself with the base material. I'll try petrol next time I come across it, methyl chloride and the recent non methyl stuff did not soften it. Heavy wire brushing it, removed it on a test section, but also removed the top plaster with it. As its survived this long well keyed in , left it be, rather than going back to the underlying surface. No tarry smell noticed in the abbrassion process, but the glassy appearance is consistent with block tar
Paraffin is a good solvent for bitumen. But if it is that it tends to soak into the surface - and you cant paint onto it, except with more bitumen.
NT
Yes, no difficulty lifting the old paint off this old surface but could not go any deeper.
My guess would be "paint" rather than bitumen.
Strictly, "stove enamelling" is a coating which is cured by heating in an oven. The expression may be used for organic coatings where temperatures of ~ 150 C are used to drive off solvents and/or polymerise the resins, or for true enamelling where a glass-based product is fused on to a metal surface at maybe 700 C (like glazing pottery).
If you blow-lamp torched a stove-enamel preparation over a surface and thickness that could take that amount of heat transfer for a relatively short time, give something like a virified surface, well bonded into a porous base structure
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