| Résumé : |
I have mentioned in the earlier chapter an outline about how the Bases are categorised. Now we will see how to categorise them. In short each base will be used to tint a particular spectrum of shades. All of them are categorised as Base I, II, III and Dark Base (D-BASE) or Clear Base. Some types of paint may not have three bases due to limited spectrum of shades they wiII be used for tinting. For example Base I is used to tint to get all light or most of the pastel shades, as it contains higher percentage of Rutile. Base II is used to tint and get slightly darker shades than the pastel shades, Base III will give comparatively still darker shades than Base II, and D-Base is used only for tinting to get the dark shades, like Dark Mikado, Terracotta, Mogul Green, Dark Green or Pinewood Green etc and the list goes on. Hence as said earlier the formulator has a tough job to formulate with the correct percentages of Rutile and Extender Pigments and Emulsion, in order to get the shades accurately at the same time economically without the use of higher percentage of tinters. In other words, every paint manufacturer makes multiple bases into which tinters are added at the point of sales. What is common to all is that the bases have decreasingly less white pigment in the "deeper" bases. If you paint with one of these bases without tint, you will get an extremely poor covering paint. A "deep" base paint will have I iterally no white pigment in it, however, acrylic paints look white in their wet state but dry and clear. If you should paint with a deep base without tint, you are essentially putting on a coat of acrylic varnish. A white tint base will have the full complement of white pigment in it, but its coverage will be somewhat lacking. Even a few drops of raw umber or black tinter will dramatically increase its coverage. Pigment does increase the protective value of coatings. A solid hide exterior stain will give far superior protection to wood over that of a semi-transparent stain because the higher concentration of pigment blocks the sun's UV rays. |
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Category of paint bases in PAINTINDIA, Vol. LXIX, N° 3 (03/2019)
