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.

  1. April 2, 2009, 10:39 am

    Where can I get these products? Sounds like one solution.
    Thank you
    PS looking for a light yellow tortoise cap for my Pelikan 400nn c. 1957. Any help would br greatly appreciated.

  2. TAO
    April 2, 2009, 10:53 am

    Sorry I didn’t put a link in there for this stuff. It’s here:

    A for your cap I’d recommend trying the Fountain Pen Network or Pentrace boards (links are along the side). The people there are very helpful with requests.

    Thanks for the comment!

  3. April 2, 2009, 11:33 am

    Tao, Many thanks for your prompt reply. Pen people are cool people!
    What I need is an address or an indication as to where to make this purchase. I tried google but no luck. There was a site but it is not functioning now.
    As for the 400nn well I ‘ll keep trying all the sites. Thanks again

  4. TAO
    April 2, 2009, 2:50 pm

    I don’t know if the Pensbury folks sell via any dealers or the like. Here’s an email address you could make inquiries to:

    Their address is listed as:
    Pensbury Manor, 22 Saratoga Lane, Alamo, CA 94507

    Sorry the link above wasn’t working for you.

  5. September 15, 2009, 1:55 am

    Hi TAO, very interesting. So this is the dye process. I have no idea how discolored the W52 is, but I hardly ever resell vintage pens I like for their antique value, so this remains an option 🙂

  6. February 17, 2010, 11:34 am

    Very useful photos!
    How has the result held up since the application of the dye?

    1. TAO
      February 17, 2010, 2:01 pm

      The pen I treated and occasionally carry has held up quite well. I’m certain that over time some may wear off depending on how much the pen is used.

  7. mike young
    May 4, 2011, 2:48 am

    I TRIED this dye on a washed out looking pen…???????THE RESULT WAS INCREDABLE …….THE PEN LOOKS LIKE NEW……Unblieveable result….people find it hard to believe my pen is 99 years old.

    1. TAO
      May 4, 2011, 11:39 am

      I’m happy you had good results. It’s nice to find a product that does what it says.

  8. Andy
    February 14, 2013, 3:03 pm

    Hi Tao, not sure if you are still replying to this post but I am currently using the PMBHRPPNo9 to blacken some of my pens now, and I am just wondering, how exactly did you buff afterwards? I have slightly too much on some parts of the pen and just buffing with a dry cloth wasn’t doing anything… Am I suppose to use a polishing agent or something (The instruction also says you can use a Jeweler’s cloth)…Is the buffing suppose to remove any unbound dried dye from the pen, because right now the pens don’t look very natural… Thanks in advance.

    1. admin
      March 1, 2013, 1:49 pm

      It’s not an easy process and the key is application. A thin, even coating and a very clean pen is required. If you have too much on some parts it’s going to be hard to make the surface even since you’ll wind up buffing the low spots next to the high spots if you do it by hand. A jeweler’s cloth is impregnated with an abrasive so it’s going to take off a lot of material and maybe even hard rubber if you are not careful. I just used a cotton cloth to clean and shine the pen after. Also you may want to try some carnauba wax.

      1. Tom
        March 24, 2013, 8:15 pm

        Hi Tao, thanks for the article, very useful. I have usually avoided BHR pens as I have never found a good solution. For BHR parts with no imprints I usually use a small amount of metal polish to remove any major oxidisation.

        I have an Onoto The Pen in BCHR and totally agree when you talk about affecting a pen’s value or collectibility through unnecessary restoration. For a pen that is 80 years if not more the discolouration on my Onoto is very minor and it’s imprint near perfect. I found that applying and buffing silicone grease with a soft cotton cloth and left to absorb adds not only a shine but a shade darker to the pen and application of Renaissance Wax Polish will add a finishing shine and protective layer after.

        I have recently come across an old Parker DQ and it is horribly discoloured. In this situation I feel there is nothing to lose and I thank you again for your informative article as I will certainly see what results can be achieved.

        I wondered if you knew of anyone offering the G10 service also? This obviously comes at a greater cost than the PMBHRPPNo9 but would be interested in talking to someone who offers it. Any help would be greatly appreciated.

        Thanks again and best wishes,

        1. admin
          March 28, 2013, 5:47 pm

          Thanks for the information on how you improve your pens appearance. I often use carnauba wax which can give a nice shiny surface. I’ve no advice to give on the G10 service since I’ve never use anyone for that. The FPN forum probably could be searched for peoples opinions of those who supply the service. Thanks for stopping by.

  9. John
    March 1, 2013, 12:20 pm

    This is great I can’t believe how great of a job it did I used it on my pen looks like new. Next I’ll use it on my bike.

  10. Jacob
    July 20, 2013, 3:50 pm

    Hallo Tao,

    I have afew questions idid not see in this fórum.
    1.When i fill up some cracks does thePMBHRPPNo9 stick with the glue(cyanide acrylaat or urushi)and blackening the repairings?
    2.Or can i mix the glue with the PMBHRPPNo9?
    Thank you,hopefuly you have an reply.

    1. TAO
      August 1, 2013, 12:53 pm

      I don’t think that PMBHRPPN would react the same on different surfaces. It was designed for black hard rubber so I’d only use it there. As for black glue I have tried to make one using black pigment and not PMBHRPPN. It was OK but since it was cyanoacrylate based there was too little time for mixing and use. There are black superglues I want to try like “Vibra-TITE 310 Toughened Superglue: Gap Filling Black” but I’ve not done so yet.

      Good luck and thanks for the questions.

  11. Keith
    September 1, 2013, 3:41 pm

    Did the application build up on the surface, or all sink in? Did it make it harder to read the imprint, or reduce the depth of the chasing?

    1. TAO
      September 12, 2013, 2:49 pm

      This is a coating so you have to be aware that if you apply it over and over it will build up. The liquid is not very thick so using it properly doesn’t cause a visible difference.