Lingerie blue
Bluing (also bluing , Neublau ) are colorants for compensating Ver turn yellow from different causes mainly for white textiles . They are the predecessors of optical brighteners .
history
Since 18./19. From the 20th century to the 1950s, so-called wash blue in the form of tablets, powder, paper strips or paste (5–10 g per 5 kg of laundry) was added to the water for the last rinse.
Linen blue has been used in large quantities for laundry care since its industrial manufacture around 1840. In the period from 1911 to around 1930, it was recommended to add 2% phenol for disinfection . Optical brighteners are added to modern laundry detergents for the whiteness of the laundry. Since these replace the missing blue light component with fluorescence , their effect is naturally much more effective.
chemistry
The tablets and powder consisted mainly of pressed cornstarch that with the mineral pigment ultramarine , rarely, indigo carmine , with other blue coal tar dyes or Prussian blue was mixed. These dyes are readily soluble in water; in the case of the pigments, they had to be finely divided and are therefore readily dispersible and can be washed out easily. Excessive concentrations lead to a blue discoloration, which can be removed with citric acid . The advantage of these coloring agents is that they do not attack fabric fibers.
Lime soap is a reaction product of sodium and potassium soaps in detergents with the calcium hardness of water. It has a dirty yellow to brown hue. The so-called Gilb are degraded fiber components or decomposed fiber auxiliaries which have a very broad, unspecific absorption maximum in the short-wave range up to the ultraviolet .
physics
The accumulation of various substances of organic and inorganic origin, but also changes in the textile material itself, usually cause a discoloration that appears to the human eye - depending on the intensity - as slightly yellowish to brownish.
Possible causes are: deposits of lime soap , rust from water, rock, iron accessories, humic substances from earth, substances from food, plants, animals, or even from humans. Decomposition of the fiber itself through oxidation , overheating when ironing .
If the discoloration does not appear in the form of spots, but rather over a large area, it is referred to as yellowing. The reason for the appearance of a yellow tone is the absorption of short-wave (= blue) parts of the spectrum of white light.
The “blue” dyes in laundry blue, on the other hand, absorb light in the medium and long-wave range of the spectrum, i.e. red and yellow.
Yellowish discolored (white) laundry can be trimmed back to white with a suitable dose of laundry blue - the complementary color . From the common point of view of the 3 color-sensitive receptor types in the human eye, the light reflected by the laundry is balanced again, i.e. white.
The laundry now absorbs the same proportions on average in all 3 spectral ranges. The color is neutral. However, the brightness has continued to decrease. The sense of sight can only perceive brightness very imprecisely; in a comparison of two laundry samples directly next to each other, the light colored laundry sample would be perceived as white and the yellowed one colored blue as darker, i.e. gray. If an even lighter pattern is added, the two original fabric patterns appear as a lighter and a slightly darker gray.
effect
White is perceived as a body color if the color stimulus affects all three cones in the eye equally. Lower intensity, i.e. a dark, therefore gray, white is subjectively viewed as purer and cleaner than a color cast in yellow.
Yellow degradation products from the manufacturing process or from aging absorb in the blue. Such contaminants arise in cotton through fiber impurities or through aging. The fiber glue from flax interferes with the production of linen . Lime soap will yellow the laundry. In paper production, the whiteness is disturbed by the lignin components or by the yellowing when lying in the light. The "yellow" is a tinge of yellow or brown. This means an “excess” of intensity at the long-wave end. On the other hand, there is no intensity in the blue spectral range (at the short-wave end).
The simple trick of laundry blue is to add a blue dye to compensate for the annoying yellow tint. In this way, all wavelengths of the light are reflected evenly again, so that the color impression is white. However, the intensity of the reflected light is lower, which can be perceived as graying under certain circumstances.
Recipes
In the Netherlands litmus was previously used as laundry blue.
Extracts from manufacturing instructions for druggists:
- Wash blue paper
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- W. Stein, Polyt. Zentralblatt. 1868, p. 190.
Brush paper strips with indigo carmine or ultramarine in a solution of 1 part carrageenan and 40 parts water as a binding agent.
- Wash blue balls
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- Magazine paint and varnish. 1912, p. 378.
Rub 100 kg of ultramarine with a solution of 6 kg of gum arabic, 6 kg of grape sugar, 7 kg of dextrin and 20 kg of potato starch until you get a putty-like mass that comes in the form of balls or sticks in the drying cabinet and is dried enough that the pieces sound when striking each other.
- Wash blue tablets, foaming
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- DRP 12 810 & FP 457 884
A mixture of ultramarine with sodium carbonate and tartaric acid with the addition of talc is pressed into molds. "Note Dissolution with the mechanism of effervescent tablets . "
literature
- GA Buchheister: Handbuch der Drogisten-Praxis Volume I. Verlag von Julius Springer, Berlin 1895.
- Buchheister, Ottersbach: Book of Regulations for Druggists Volume II. Springer Verlag, Berlin 1933.
- Dr. O. Lange: Chemical-technical regulations. Spamer publishing house, Leipzig 1916.