![scar stock crack forum scar stock crack forum](https://i.imgur.com/Zm8RH39.jpg)
This sounds like a lot of work but with practice can work very well. This will help reduce the risk of future cracks both to your repair and to the rest of the original plastic and will also help make the lip even all the way around. If the crack was on the lip of a cap or barrel and the very edge of the lip is quite thin you may want to also reduce the edge of the lip slightly to make the edge a little thicker. Depending on how much material I need to remove and how rough it is I will start with either 2400 or 3600 micro mesh and wet sand it working down through 6000, 800 grit to finish it and give it that beautiful smooth new plastic sheen. Once it is set and you are happy with the fill I then mask off around the fill with scotch tape so you do not damage other areas as you wet sand the fill back to the original shape. This also helps to shape the mixture so that once it sets it is easier to get the natural shape of the pen back during finishing. While the powder and solvent are still soft I then condense it and press it into the crack further by rolling a smooth piece of metal over the pile.
![scar stock crack forum scar stock crack forum](https://media1.cgtrader.com/variants/ySPt7PxaveLKiwYE8apHi8qD/e44aa6a6359827c9089792cde0c079681b83d3b5c3037cc0525c25607e54355b/screenshot000.png)
I pile the plastic powder carefully into and around the ground out crack and then after drop the solvent onto the pile of powder with an eyedropper that has a nice small opening. I have found that taking old broken clear plastic Parker Vacumatic plungers and sanding them with a 220 grit sanding block makes a nice fine powder that due to it's clarity will be unnoticeable with most semi transparent celluloids. I have found this to very difficult and slow and the powdered celluloid tends to be chunkier and hard to work with. Many have suggested scraping the inside of the cap to get powdered celluloid that can be mixed with the solvent in order to fill the beveled crack. In order to make a stronger repair you will need to bevel the edges of the crack and refill it with celluloid. If the celluloid is quite thick and subsequently there is a large mating surface to both sides of the solvent by itself may work adequately for strength but do the slight melting of the plastic by the solvent you will have a slight depression to the edges of the crack and would then have to smooth it out to reduce noticeability. Because the chemical is a solvent and not a glue just applying it to a crack may not work very well. Testor's 3502 (standard model cement) is a mixture of acetone and methyl ethyl ketone When I asked American Art Plastics (a celluloid manufacturer for fountain pens) what they would recommend for bonding celluloid they recommended either acetone or methyl ethyl ketone. To chemical weld celluloid there are 3 chemicals that can be used Now I can only comment on repairing cracks in celluloid as that is all that I have worked with so far but here is what I have learned I am also fairly new to vintage pens repair and restoration but I have had occasion lately to do a lot of research and experimentation with crack repair.