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Cleaning technology No. 5 |
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The movement of dirt |
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The problem of exudation of color from patterned textile products is called bleeding, and to test for the possibility of the occurrence of this, there is the "bleeding test." The patterned material
to be tested is attached to the end of a long, narrow piece of material and is suspended with its end dipped in a solution of weak nonionic surfactant. When the solution advances upwards due to capillary
action, the occurrence of bleeding is detected through the ascent of colored liquid.
This is also called the Daimaru method, possibly because it is a testing method developed by the laboratories of that department store.
If there is an affinity for the long, narrow fabric, the advance of the liquid will be slower and the color will stop lower down. Conversely, if there is no affinity, it will be observed that the
color will move up to the same height as the liquid.
In the movement of dirt that remains after the drying which follows dry cleaning, incorporation of this idea is worthy of consideration. Dirt with a high affinity for the cleaning solvent is considered
to have a low affinity for the fabric, and so is transported to areas where the solvent dries, and is left there when the solvent has dried, appearing as a stain. A solvent is a mix of molecules of
different weights, so there are different levels of affinity, and thus it is useful in preventing the appearance of stains. It is not the case that pure is good.
(T.T.)
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