Restoring Black Hard Rubber Using The World’s Longest Acronym

There’s no way getting around the fact that a lot of vintage pens are made of hard rubber. Before the dawn of plastics it was one of the best materials for the job. Light and strong it’s made when rubber is mixed with sulfur and then cured by heat. Once it’s lathed into a cap and barrel it was often made more esthetically pleasing with heat embossed decoration. Eventually brighter colors, sometimes in patterns, were developed to spruce the “any color you want as long as it’s black” pens up. All those benefits made hard rubber popular for many years until it lost the battle with the early celluloid plastics.

There are negatives as well to hard rubber. One of the worst is that over time the material will discolor to brown or sickly olive green. This is caused by exposure to UV light which oxidizes it as well as exposure to moisture which bonds with free sulfur and creates sulfuric acid on the surface. Either way with time it’s enviable that the surface will sooner or later take on the new and unattractive cast.

It used to be you couldn’t do much for an old pen that wasn’t shiny black anymore but accept it. Buffing the surface exposed undamaged rubber but at the cost of loss of pattern or imprint detail. Black paint lost detail as well by building up a coating on the exterior. If you lucked out and got a mint BHR (black hard rubber) pen you kept it in the dark or used it and took your chances.

Happily a few years ago two methods arrived that promised to restore your drab discolored pens to black beauties. With the process called G-10 a dye is infused into the material and gives it new color. It’s not reversible after application and has to be performed by someone who offers this service. Proponents claim that this makes the newly treated rubber resistant to further damage by blocking UV light and closing the pores in the material against moisture. The other option is Pensbury Manor Black Hard Rubber Pen Potion No. 9 (known from here on out as PMBHRPPNo9) which is a self applied dye. It’s a treatment which is lightly absorbed into the pen’s surface to blacken and protect it in a similar manner to the first process. The coloring can be reversed by using an ammonia/water combination to remove it.

Why are we discussing this? Well, I have a Wahl eyedropper that exhibits a very slight amount of discoloration on one side of the barrel and cap. It was bothering me a bit and since this is not a rare pen I thought I’d finally give re-blackening a try. Since I like to do things myself as well as save money the PMBHRPPNo9 seemed to fit the bill. I ordered it and when it came I decided to first try it on an old heavily discolored pen cap I had in the parts pile. What follows are pictures and text showing this test and the results.

Below is what the PMBHRPPNo9 looks like brushed onto white paper. The washed out look of it doesn’t lead you to believe it will do much to darken the hard rubber.

Hard ruber dye on paper

I used a knock out block and a dowel to hold the cap in an upright position for application and drying (it’s recommended you let the treated parts cure for 8 hours). In the first picture you can see the PMBHRPPNo9, block, brush and untouched cap.

BHR dye components

If you look at the close up of the cap you can get an idea of how much it’s turned brown. Before starting you need to clean the parts in an ammonia and water solution so it will be free of oils and other surface contaminants. If you don’t the dye may not bond properly.

Pre-dye cap

Application is as simple as dipping the brush into the solution and applying it in long, even strokes.

Dye application

After curing I did a little buffing with a cloth to shine up the new surface. In this picture you can see that the section I worked on did indeed get much blacker and shiner.

Post-dye cap

While not looking exactly “from the factory” fresh, the part of the cap PMBHRPPNo9 was applied to is much more appealing. Of course it’s probably not a good to do this to rare pens where their value might be decreased by messing with the surface. Another thing to consider is that some collectors think any cosmetic changes like this are unacceptable since the natural state of the pen is changed and it could be represented as being in better condition than in actuality. Overall, the process seems like it did not do any damage to the rubber substrate and had very positive visual and tactile result. Not bad if it fits your needs.