How to repair chipped bakelite

Chip, unrepaired
Chip, unrepaired

A small bakelite chip can really be an eyesore. Here is a simple method for repairing such damage. Please beware that this method is not reversable. You’ll have to grind away the material applied to the bakelite if you are not happy with the result, in effect making the damage greater. So be very sure that you really want to do this.

Think before you act: do you really want to repair it?

Please consider whether you really want to repair that chip. After all a telephone made of bakelite is decades old and has often seen the better part of a century. So wear and tear is to be expected for an object that has seen daily use for decades. It ads to the character of the telephone and is part of its history.

What are we going to do?

Epoxy resin, pestle and mortar and Norit
Epoxy resin, pestle and mortar and Norit

We are going to apply epoxy resin to fill in the missing chip. The patient in this case is a Standard type 1954 wall phone, with a small chip from the top right corner.

The resin will be cast in such a way, that it forms one piece with the bakelite and follows its original shape exactly. Before casting we are going to color the resin to match the bakelite.

In this case we have black bakelite. Colored bakelite and white bakelite is far more difficult. It will need to take a lot of testing beforehand to get the color right.

What do we need?

  • epoxy resin, in the form of 2 component glue
  • toothpicks
  • a piece of paper to mix the glue and the color

    Active charcoal tablet, ground to a powder
    Active charcoal tablet, ground to a powder
  • coloring powder, in this case Norit, ground to a fine powder
  • clear tape. Do not use the cheap thin tape, but the strong thicker kind

Step 1, clean and polish

Before we can start applying the resin the bakelite needs to be washed. If there is dirt on it, the resin will adhere to the dirt and not the bakelite thus forming a weak bond. I wash the bakelite in warm water with washing up liquid.

I brushed the edges where the chip is missing thouroughly with a brush. Please mind that in the example here, it was an old chip. So there was dirt on the surface where the chip broke away.

Also polish the bakelite before repairing it. Polishing afterwards may damage the resin cast, because it needs time (days!) to harden. Also you can match the color of the resin better if the telephone is polished.

After polishing, clean the fracture surface again.

Step 2, making the mold

Applying the tape
Applying the tape

I use tape to keep the liquid resin in place until it has hardened. With tape you can follow the shape of the bakelite exactly. Even simple curved surfaces can be repaired in this way. More complex curves cannot be repaired in this manner.

Please make sure there are no folds, creases or fingerprints on the tape, where the chip is missing. These will make an imprint in the resin.

I test fit the tape carefully, and peal it away partly before applying the resin.

Step 3, mix the resin with the color

Resin and powder
Resin and powder

As I am repairing black bakelite, I use Norit tablets. They are made of activated charcoal. I grind them to a fine powder using a pestle and mortar. If the bakelite is stil nicely black and shiny this will make a good color match. If the bakelite is somewhat faded, you’ll need to mix in some grey.

Mixing the resin and charcoal powder
Mixing the resin and charcoal powder

For colored bakelite you may want to try out coloring little bits of resin first to get a good colormatch, before you do the actual repair.

A ratio of about 1 part Norit powder to 10 parts resin is enough to color it black.

Step 4 apply the resin

Applying the resin
Applying the resin

When applying the resin you have to work quickly, otherwise the resin becomes too thick. You have about 20 min, which is quite enough time.

Please mind that the tape is peeled back, before applying the resin.

With a toothpick I cover the edges in a good layer of resin. Make sure the resin is right up to the edge, covering the total fracture surface.

Ready for more resin
Ready for more resin

Then put the tape back over the bakelite. Make sure the tape is straight. Be carefull, if you put the tape on it may warp. You’ll end up with a wavy surface of the repair. So double check that it is straight and even. You can use the reflection of a lamp on the tape to check this.

Then, with a toothpick, apply more resin, working your way from the resin you already applied up to the edge of the bakelite.

All the resin has been applied
All the resin has been applied

Rub the toothpick over the inner surface of the tape, where it is covered with the liquid resin. This will remove air bubbles from the surface.

When you have applied the resin, leave the telephone to rest. You may need to support your telephone in a certain angly to make sure the resin does not run off.

Step 5 waiting and removing excess resin

Tape removed
Tape removed

Then wait at least 24 hrs before removing the tape.

After that you will need to remove the excess resin and smooth down the edge. Please make sure the resin is hard enough, otherwise it will warp and deform.

And voila: hard to tell there was ever a chip, don’t you think?

See also this article on how to repair cracks in bakelite:

How to repair a small crack in bakelite

Was there ever a chip missing?
Was there ever a chip missing?

14 Comments

  1. Really bravoo that’s is great because the restoration my hobby about 30 years ago and i did that i lot times with bakelite without to learn but when i saw some one do that really i am happy because some people did right thing in the world. Hope you good luck

  2. That is a beautiful fix! I collect/hoard/restore old radios and vintage electronics, and this method works perfect,I tried it on restoring a rotary knob I could not find a replacement for, and your process worked just as good in that application! It is even machinable and can be polished a bit after.

    Thanks for sharing a great tip!

  3. wauw geweldig! zo eenvoudig en met zo’n goed resultaat. Ik heb een nog functionerende telefoon, dus goed om te weten dat dit nog kan. Bedankt voor de goede en gedetaileerde uitleg!

    • Hi Donna,

      Thank you for your message. I’m sorry, I have very little time for anything besides phones. I cannot find the time to repair your tiles.

      I doubt that it would be economic to have them repaired by me anyway. Nor would the repair withstand actually playing with these tiles.

      Groeten,

      Arwin

  4. I have a brown bakelite radio which had a large piece broken. I glued that in place (using very runny cyanoacrylate glue and corn starch, a trick I learned from joining Corian. The corn starch acts both as structural filler and provides capillary action to draw the glue in).

    Now that it is set, I am wondering how I may hide the crack line and fill in the few missing chipped bits. I thought perhaps I should cut a piece of Bakelite from an invisible part, grind it to a very fine powder, sprinkle and pack it tight into the crack line then whisk in some cyanoacrylate. Once it sets, I will sand it smooth.

    How do you gage my chances of success?

    • Hi Alain, mixing bakelite powder with glue, to match the colour is a method I have heared about. I do not have much experience with it myself, certainly not with colours other than black.
      I would try a drop with powder on the inside, to see if the colour really matches. If it does, it should be possible to make the crack and chips disappear.
      Regards,
      Arwin

  5. I have a toaster of bakalite and steel mix.
    Suddenly todter fell down and one side handle of The toaster is broken. How to repair bakalite handle of toaster. Please suggest me.

    • Hi Sachin, that very much depends on the type of handle. I would use superglue (Cyanoacrylate). But as it is a handle and I do not know what it looks like, I do not know if a repair like that is solid enough for the handle to be used without breaking again easily.
      You could reinforce the repair by drilling small holes in both piece and fitting a metal reinforcing bar.

      Or, if the model is not too uncommon, source a replacement handle from somewhere.

      Regards,
      Arwin

  6. Dear Arwin,

    your suggested solution is as simple as it is clever!

    I’m currently dealing with a fairly young Siemens W38 of 1950 (yes, it’s true) which of course has chipped body edges… I guess you are familiar with this particular problem, as the german post office required the bakelite body to cover the base plate which in hindsight was a pretty stupid choice regarding mechanical resilience due to the thin bakelite being likely to chip… however, I’m wondering if
    a.) the resin method will succeed in this application and
    b.) what your thoughts are on the slanted sides of the W38’s lower body. Of course the cipped area includes the round corner so I’m slightly concerned about fixing the mold with tape as it must both cover the radius and the slant.

    One may of course argue about what is the point in retaining the body and not replacing it by just another W38/48 body of which there are plenty, but as it happens the phone – though witnessed a rough past – is still completely consistent of its original parts which I find to be most appealing from the collectors perspective. The body even has the Siemens-decal still intact, so replacement of this is difficult to achieve.

    I have another point: I wondered about the dial on your otherwise magnificient M&G Weltruf. I do find the Siemens-dial rather unsatisfying as is somewhat ruins the aesthetics. Luckily though, the number plate of the dial is still intact so you might try to recast the dial using black coloured resin? I have some ideas on that… 🙂

    Kind Regards,
    Alex

    • Thank you very much, Alex. I think the resin will work on the edges of that W38 housing. I think the resin will be less prone to chipping than the bakelite itself.

      To do a corner, especially if it is bigger chip, will not be easy. The tape is prone to warping, leaving a misshapen repair. I do recommend to get good quality thicker tape. That holds its shape better. And you may want to put two or more strips of tape over each other, to make it even thicker.

      I can relate to keeping the original body shell and your reasons for that. I myself do not like to swap out parts like that.

      With regards to my Weltruf dial (see here for other readers: http://www.matilo.eu/3-the-phones/1926-1945-bakeliet-ww2/mix-genest-weltruf/?lang=en) > the dial I have put on it now, is the best I had available. It is just a place holder.
      I am thinking about how to repair the old one. I was thinking of getting a sheet of black plastic, perhaps even bakelite, and making a new fingerwheel. And then putting back the old inner part of the original fingerwheel, with logo and numbers.
      But I may need a lathe for what I was thinking. So I need to make friends with somebody who has something like that. 🙂
      Regards,
      Arwin

      • I have given it some thought on how to achieve the round corner and warping certainly is a difficult issue there. For now, I am thinking about abandoning tape for that purpose and use light cardboard and a glue stick. I will have to give the resin some sort of finish anyway, so I suppose I could do with the rather rough surface cardboard will create. About the variance in radius, I guess I will have do come up from both sides of the corner and have the cardboard’s edges not parallel to the shell’s edge, but askew, ascendingly. In my spatial imagination that might work for this particular situation.

        About the finger wheel, I’m not quite sure if you’ll succeed lathing bakelite. If you look closely at any bakelite finger wheel (which I suppose you did many many times already), you’ll discover the finger holes still bear slight marks of the mold that were removed in the finishing process (most prominently on the rather thick wheels of the German bakelite N38). To manufacture Bakelite as private individual is not entirely impossible but is very difficult if you are in fact not aiming for a pink sponge (which in fact was the result as back in school I nudged our teacher a good deal in order for us to actually make bakelite as we dealt with plastic compounds in chemistry) but rather for uniformily shiny black bakelite. You will have to experiment on different ratios of formaldehyde, phenol (as its common market law anyway, I don’t suppose there’ll be many differences in purchasing these, which is quite impossible here in Germany for private persons…) and respective additives like sud and saw dust, temperature and pressure and of course the mold that needs to be treated in a specific way to ensure it will release the part and give it a natural shine. So in conclusion: any pleasant bakelite surface was molded and not lathed or threaded afterwards, meaning that you won’t be happy lathing your finger wheel. For a quick taste: look at the edges at any bakelite shell where you may discover they bear the disk saw marks to remove excess material. Other sorts of plastic today are mostly thermoplastic and they too aren’t very tolerant to machining, either, as they are quite sensible to temperature of course.

        I’ve got another idea, if you could get to like the finger wheel to be made of metal (which, as you know, was very well contemporary to this phone): Look for small metal workshops that still train apprentices and ask, if they will be willing to fashion a new finger wheel. As this includes all necessary steps from measuring and designing to lathing, drilling, filing and finishing, I suppose they’ll be quite happy for such a job.

        Also, I’ve got a request, if you are interested: If you were interested in making a review on the M&G-Dial of the Weltruf regarding the technical aspects, including the mechanism. Thanks to the corona virus, I’ve had great reveiling moments on the Siemens Dials (proto N30, N30 and N38) as well as on the Merk/T&N Dials and I would appreciate getting to know other makes and manufacturers. What interests me especially is the way the run speed is adjusted, as I’d like to understand the “universal principle” behind. 🙂

        Have a nice week end!
        Alex

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