Masonry Magazine March 1971 Page. 22
A poultice is a cleaning method that involves applying a paste-like mixture to a stained area. This mixture typically consists of a solvent or reagent and some inert material. The inert material may be talc, whiting, fuller's earth, bentonite, or some other clay. The solution or solvent used depends upon the stain to be removed. Enough of the solution or solvent is added to a small quantity of the inert material to make a smooth paste. The paste is smeared onto the stained area with a trowel or spatula and allowed to dry. When dried, the remaining powder is scraped off.
A poultice cleans by much the same type of action as takes place when efflorescence occurs. The solvent in the poultice dissolves the offending stain on the brick. The resulting solution then migrates to the surface of the poultice where the solvent evaporates. The stain is left on the loose powdery residue and can be removed along with it. Repeated applications may be necessary since all of the stain may not dissolve the first time. The chief advantages of poultices are that they tend to prevent the stain from spreading during treatment and they tend to "pull" the stain out of the pores of the brick.
If the solvent used in preparing a poultice is an acid, do not use whiting as the inert material. Whiting is a carbonate which reacts with acids to give off carbon dioxide. While this is not dangerous, it does make a foamy mess and destroys the power of the acid.
TABLE 2
Sources of Cleaning Agents
| Cleaning Agents | Source of Supply |
|---|---|
| Aluminum chloride | Available from your pharmacist. |
| Ammonia water | Household ammonia water available at the super market. |
| Ammonium chloride | Salt-like substance available from your pharmacist. |
| Ammonium sulfamate | Not now readily available. Was used as base in weed killers. Now substitute any weed killer solution as marketed by nursery and garden supply stores, use according to directions on the package. |
| Coustic soda | A material capable of destroying or eating away by chemical action. Use any of several brand-nome substances, such as "Drano", available at the super market. |
| Kieselguhr | Diatomaceous earth; not easily available. |
| Lime-free glycerine | A liquid available on the counters at drug stores; usually used as a base for hand lotions. |
| Powdered pumice | Available at hardware stores for use as a sanding or polishing material. |
| Sodium citrate | Looks like enlarged solt granules; purchase from your pharmacist. |
| Sodium hydrosulphite | A white salt available from your pharmacist, or it is the "hypo" of photographic fixing agents. |
| Talc | An inert powder available on drug store counters as "purified talk"; or substitute bathroom talcum powder. |
| Tricloroethylene | A highly refined solvent. Purchase dry cleaning solvent from service station or super market. |
| Trisodium phosphate | A strong base type powdered cleaning material sold under brand names by all paint stores and some hardware stores. |
| Whiting | A powdered chalk used as a pigment in pulty and cold-water points. Available at paint manufacturers, or possibly some large paint departments. If purchase is too difficult, probably kitchen flour would suffice. |
Paint Stains
For fresh paint, apply a commercial paint remover, or a solution of trisodium phosphate in water-2 lb of trisodium phosphate to 1 gal of water. Allow to stand and remove paint with scraper and wire brush. Wash with clear water. For very old dried paint, organic solvents similar to the above may not be effective, in which case the paint must be removed by sandblasting or scrubbing with steel wool.
Iron Stains
Iron stains are quite common and, in some cases, have covered entire walls. These stains are easily removed by spraying or brushing with a strong solution (1 lb per gal) of oxalic acid in water. Ammonium bifluoride added to the solution (1 lb per gal) will speed up the reaction. The ammonium bifluoride generates hydrofluoric acid which etches the brick. This will be evident on very smooth brick and, therefore, should be used with caution.
Alternate Method. Mix 7 parts lime-free glycerine with a solution of 1 part sodium citrate in 6 parts luke-warm water, and mix with whiting or kieselguhr to make a thick paste. Apply paste to stain with trowel, and scrape off when dried out. Repeat until stain has disappeared and wash thoroughly with clear water. A poultice made from a solution of sodium hydrosulphite and an inert powder (such as tale) has also been used for the removal of iron rust stains.
Copper or Bronze Stains
Mix together in the dry form 1 part ammonium chloride (sal ammoniac) and 4 parts powdered talc. Add ammonia water and stir until a thick paste is obtained. Place this over the stain and leave until dry. When working on glazed tile, use a wooden paddle to scrape off the paste. An old stain of this kind may require several applications. Sometimes aluminum chloride is used in the above procedure instead of the sal ammoniac.
Welding Splatter
A problem related to iron staining is welding "splatter". When metal is welded too close to a wall or pile of brick, some of the molten metal may splash onto the brick and actually melt into the surface. The oxalic acid-ammonium bifluoride mixture, recommended for iron stains, is particularly effective in removing welding splatters. As much of the metal as possible is scraped from the brick. The solution is then applied in a poultice. When the poultice is