Bleaching Woodstocks and Topcats

[PANAMATIK]

Everybody knows, that the plastic cases of many calculators are sensible to sunlight and get brown over the years. After having found an interesting website about bleaching with Hydrogenperoxide I tried to bleach my HP97.



I made these two photos, one before and one after a two day bleaching, for comparison both with a normal grey woodstock case on the left. But I was very careful and didn't bleach very long and used only 3-6% H2O2, thus I added some water.

Sunlight or UV light accelerates the bleaching process, but is not necessary if you have time.

For needing less liquid to cover the big HP-97 case, I added glass marbles, to rise the surface level. It does not have any chemical influence.



The ugly brown color is now grey again and looks much better than before, however my results are not perfect, because some parts became a little patchy, but this is even more visible on the photo than in real. I think this effect can be minimized, if the case is cleaned very well with a fat solvent before the procedure. Or it will vanish after extensive bleaching with high concentrate 30% H2O2 until the case is completely light grey. I did not yet test this approach.

But experiments shall be continued

Bernhard