Bluing (fabric)

Blue laundry (washing blue, also Neublau ) are brightener for white textiles.

History

Since 18-19. Century to the 1950s, was given when washing so-called bluing in the form of tablets, powder, tape or paste ( 5-10 g to 5 kg of laundry ) in the water of the last rinse.

Wash blue was used since its industrial production in 1840 in large amounts for laundry. In the period from 1911 to 1930 was recommended for disinfection add 2% phenol. In modern detergents, optical brighteners are added to the whiteness of the laundry. Since replace the missing blue light component by fluorescence, their effect is naturally much more effective. Ultramarine blue was the usual raw material for the production of laundry blue.

Chemistry

The tablets and powder consisted mainly of extruded cornstarch, which was mixed with the mineral pigment ultramarine, more rarely, indigo carmine, with other blue " coal tar dyes " or with Prussian blue. These dyes are readily soluble in water, in the case of pigments they had to be finely divided and are readily dispersible, and can be easily washed out. At high concentrations lead to a blue discoloration, but this was eliminated again with citric acid. The advantage of this color means it is that they do not attack fibers.

Soap scum is a reaction product of sodium and potassium soaps in detergents with the calcium hardness of the water. She has a dirty yellow to brown color. The so-called Gilb are degraded fiber components or decomposed fiber auxiliaries, the Ultraviolet to the inside have a very broad, non-specific absorption maximum mainly in the short wavelength range.

Physics

The blue fabrics in the wash blue mask the slight gray haze, caused by deposits of calcium soap. Also yellowing, those slightly yellowish discoloration of aged wool, cotton and linen fabrics were covered. The laundry was given a slight blue tint. This blue cast acted as a complementary color to the " yellowing ", which they re-appeared white.

Effect

Is perceived as a white body color as the color stimulus acts uniformly on all three cones in the eye. Lower intensity, so a dark, hence gray white is subjectively regarded as pure and clean as a color cast to yellow.

Yellow degradation products from the manufacturing process or aging of the absorption in blue. Such impurities result from cotton fiber by impurities or by aging. In line extraction of Faserleim from flax interfere. By lime soap yellowed laundry. In papermaking, the white man is disturbed by the lignin or the yellowing while lying on the light. The " yellowing " is a color tinge yellow or brown. This means a " surplus" of intensity in the long wavelength end. On the other lacks intensity in the blue spectral range ( short-wavelength end ).

The simple trick of washing blue is a blue dye to which absorbs the annoying yellow tinge. In this way all wavelengths of light are reflected back evenly, so that the perceived color of white is made. However, the intensity of the reflected light is lower, which can be perceived in certain circumstances as graying.

Recipes

Excerpts from manufacturing instructions for druggists:

Coat of paper strips with indigo carmine or ultramarine in a solution of 1 part of carrageenan and 40 parts of water as a binder.

100 kg ultramarine with a solution of 6 kg of gum arabic, 6 kg dextrose, 7 kg of dextrin and 20 kg of potato starch rub in until you get a putty-like mass formed into balls or rods comes in the oven and as far as is dried, the pieces sound when clashing.

You pressed a mixture of ultramarine with sodium carbonate and tartaric acid with the addition of talc into molds.

In the Netherlands earlier litmus was used as a laundry blue.