This section is from the "Encyclopedia Of Practical Receipts And Processes" book, by William B. Dick. Also available from Amazon: Dick's encyclopedia of practical receipts and processes.
376. To Remove Iron Mould. The part stained should be remoistened with ink, and this removed by the use of muriatic acid diluted with 5 or 6 times its weight of water, when it will be found that the old and new stain will be removed simultaneously. This is a very effectual method.
377. To Remove Stains of Iron Mould from Fabrics. The removal of these stains is a matter of some difficulty if they have remained on a fabric for some time. The usual substances employed for this purpose (oxalic acid or quadroxalate of potassa) require placing, in concentrated solution, in contact with the material for a considerable time, thereby materially weakening and rotting the fibre. The following method is free from this objection, and will remove stains of long standing almost immediately: "Wet the mark with yellow sulphide of ammonium, by which it will be immediately blackened, and allow it a minute or so to penetrate; then wash out the excess of sulphide, and treat the black spot with cold dilute muriatic acid, by which it is immediately removed. Finally, wash well with water.
378. To Make Essential Salt of Lemons, for removing iron moulds, ink spots, and stains from linen and cotton. Take 1 ounce of oxalic acid in fine powder, mix with 4 ounces of cream tartar, and put it up in small oval boxes.
379. To Remove Ink, Iron Mould, etc.., from Linen. "Wet the finger in water, dip it in the powder (see last receipt), and rub it on the spot gently, keeping it rather moist, and the stain will disappear without injuring the fabric. After the stain disappears, wash the linen in pure water. The salt of lemon used as a beverage is simply tartaric acid, put up in long bottles. The above is poisonous if swallowed.
380. To Remove Iron Mould and Ink from Delicate Linen Fabrics. These may be taken out by wetting the spots in milk, then covering them with common salt. It should be done before the garments have been washed. Another way to take out ink is to dip it in melted tallow. For fine, delicate articles, this is the best way.
381. To take out Mildew Spots. "Wet the spots with a solution of chloride of soda (Labarraque's solution), or of chloride of lime (bleaching fluid), or with chlorine water, and they will disappear immediately. Fruit and wine stains of all kinds may be removed in this way. (See also No. 128.) Starched linen which has contracted mildew spots will require an application each day for 2 or 3 days; rinsing out and bleaching in the sunshine after each application.
382. To Remove Mildew. Mildew is easily removed by rubbing or scraping a little common yellow soap on the article, and then a little salt and starch on that. Rub all well on the article, and put in the sunshine. Or, soap the linen previously wetted, and apply salt and lemon juice to both sides; or apply finely powdered pipe clay, or fuller's earth, or finely powdered chalk. Expose it for several hours to the atmosphere.