Molding Repro Supro Butterfly buttons for Kluson Tuners

Bluesy : I am sorry I have been busy with my other passion and this promised tutorial was deleted and I still wonder if the Harmony board is the right place to explain these tricks - but as I read few posts about others guitars it seems that this contribution should be allowed in the repair section...

Chasing the Kluson-Supro Butterfly

Love is in details and the butterfly buttons around her head make the Supro Dual Tone guitar so sexy for me. Mine was missing them all…
But chasing the butterflies is not easy on the Net - They don't show much on Ebay these days...and even David help I was only able to snipe buy twice the same bass sides half set of tuners…
Once I succeeded catching a repro tailpiece so - I had contact with the french seller and after sharing infos and tricks I convinced him to send me an original part as I pretended to be able to clone the buttons with silicone molding and polyurethane resin casting so this precious half of a Supro Kluson set 3 on plate will be my master …

My little knowledge was mainly theoriclal though I am an experienced modeller and used to work with carbon fiber and epoxy.
The simplest way to make a mold is to use the 2 parts stuff a paste called here in Europe : Siligum - see how" Yolb" took the print of the Fender logo and cloned it with great success - Shop for arts & craft materals
100g for €15 not that cheap if you don't succeed at the first attempt…

I have tried to make neat molds by pressing the original buttons on the silicon paste in a plastic box - the kind you buy in DIY store for your screws parts & bits… But that doing this way, you are never sure the master button will be well wrapped around with the Silygum paste - the working time is very short - the result was not good enough for me…

Of course I was able mold my first samples with this product but I am the kind of guy that want professional results so I searched and found a better product :
the Silicone RTV- this product more expensive because you buy 1 Kilo - Accurate mixing of hardener and silicon is requiered - but a small syringe 2,5 cc and a large one 50cc ( the kind used to feed people with - no needle) is all you need to achieve the correct proportions and the optimum quantity ( Room- Temperature- Vulcanising : the silicone set within 24 hours)

But you will have to face the main problem with this RTV silicon = BUBBLES - when the product polymerised bubbles want to go back to the surface
If your button is laying horizontaly the bubbles are trapped under and one side of the mold is not perfectly smooth

Of course you can cast a button in the in this half perfect silicone mold but you certainly have to sand and polish the button to be proud - almost…

As I don't have a vacum pump I must find a trick to avoid this problem - a 2 steps process
So I decided to mold only the upper part then flipping the master ( and the half mold) to mold the other half- Then I find a better way to built a box with plastic angle 2 cm screwed on a plywood plate - I shimmed the master buttons under with a foam plate- I run the silicon over.To install the master in - I have to shim the Kluson with balsa wood
First you have to brush a first layer of silicon on the original part then running the rest of the elastomer as high as possible the air bubbles should be eliminated

No stripping agent is needed - the silicon sticks to himself : the final silicon block is seamless.

The master 3 on plate ( original parts) are extrated from the silicon parting it with a cuter blade right in the middle of the mold - I was able not to spoil the original parts Pour in the mold polyurethane resin with a syringe - mixing equal parts of polyurethane in a yogourt pot.
Fill the syringe and quickly inject the liquid in the silicon mold- only few minutes of working time - so I fill only 3 buttons each time - One thing I learned is that 2 events (holes) are not enough to avoid the air bubble on the upper part of the casting - see the first fillings were not complete
I ended to make 3 events : one hole for filling the others to see the resin pouring out - this RTV silicon can be stretched a lot and it is easy to remove the bottons from the block - While the resin is not so hard - few minutes- I cut the overflow with my favorite nail scisors

One day a much yonger friend harased by my explainations about this delicate molding process, simply pointed that I could have better a results in a one time silicon running if I considered the vertical position. He predicted that the bubbles would slide all along the sides of the master because of the shape of these buttons…

So I gave a try for a last mold - I used styrofoam blocks to make the box around the master- (I have a hotwire foam cuter - as a modeller tool) But I am sure that you could borrow Lego bricks from your kids to built the box walls

Now a step by step showing how to bore a perfect hole for the Kluson tuner shaft
Your need to make another " master" with a perfect boring then put on a shaft in the clutch - using another silicone mold to hold the button right in place - true - square- level !?- under the drill press
You will have to substitute new fresh molded button to the "master" in the silicon mold - Of course the plastic box stays in place with double side tape under the angles…

I hope my picts are better than my tedious explainations …

july 2011

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