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Repairing a crack (plastic pen)


fpman

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I've read, here on FPN and on eBay, of 'professionally repaired' cracks in a pen. What do you use to do a crack repair like that? I found out the hard way that super glue, while effective, will melt and scar most (many?) pen plastics. And how do you 'stabilize' a crack? I have a few 'beater' pens that I really like, that make good user pens, but that have cracks in the section that allow ink to leak out. For the time being I've been able to stop the leaks using silicone adhesive but over time that peels off.

 

BTW - I did try to search the archives before I posted this but while I found a bazillion references to cracks and repairs, I couldn't find one to answer my question (though I'm sure there are plenty of them out there somewhere).

Rick B.

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To "professionally repair" a crack I send the pen to Ron Zorn who is a Professional...

Even though I do restoration professionally, I do not do pen cracks so I send them to my professional crack repairer.

There are solvents that the professionals use, but they have also spent a lot of time learning to use them properly.

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Hi Rick,

 

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.

 

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;

 

- To chemical weld celluloid there are 3 chemicals that can be used;

- acetone

- MEK (methyl ethyl ketone)

- THF (Tetrahydrofuran)

 

- 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.

 

- Testor's 3502 (standard model cement) is a mixture of acetone and methyl ethyl ketone

 

- Because the chemical is a solvent and not a glue just applying it to a crack may not work very well.

 

- 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.

 

- In order to make a stronger repair you will need to bevel the edges of the crack and refill it with celluloid.

 

- 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.

 

- I have found this to very difficult and slow and the powdered celluloid tends to be chunkier and hard to work with.

 

- 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 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. (these can be found at most hobby shops)

 

- 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. 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.

 

- 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.

 

- 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, 8000 and 12000 grit to finish it and give it that beautiful smooth new plastic sheen.

 

- 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. 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.

 

 

This sounds like a lot of work but with practice can work very well. I recently repaired a Red Parker Royal Challenger Deluxe which had a very large crack in the lip of the cap and now without the help of a loupe you can not tell there was a crack there and with a loupe it is still not easy to find.

 

Hope this helps,

Dan

"A common mistake people make when trying to design something completely foolproof is to underestimate the ingenuity of complete fools." Douglas Adams

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Dan - fantastic information. Thank you so much for sharing. I remember when you could buy Testor's Model Cement everywhere; I guess I'll find it now somewhere on the Internet.

Rick B.

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Dan - fantastic information. Thank you so much for sharing. I remember when you could buy Testor's Model Cement everywhere; I guess I'll find it now somewhere on the Internet.

 

Testor's 3502 is sold by Hobbytown, USA.

I'm hung like Einstein and smart as a horse!

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Dan - fantastic information. Thank you so much for sharing. I remember when you could buy Testor's Model Cement everywhere; I guess I'll find it now somewhere on the Internet.

 

Testor's 3502 is sold by Hobbytown, USA.

 

I located it at Michael's Craft Store (believe it's a nationwide chain)... in the aisle with the model cars and planes.

I'm still not 100% certain why I was in that store in the first place... seems horribly out of character for me.

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Pure MEK is at Tru-Value hardware and Lowes. In Quart cans which should be enough for a pen or two. :P

 

Bruce in Ocala, FL

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Solvents are great, but they can erode the plastic at the crack and can leave a cap lip pretty thin where the work was done. Sometimes this type of crack fusing with solvent alone will drag discolored plastic or other stains from inside the pen into the crack while "fusing it" and make the crack more visible. The best way to handle cracks is to add original plastic in syrup or powder coat form from scrap pieces of original matching plastic into, onto and above the crack and then let it cure and grind it down to match the surrounding surface. BUT you have to have some scrap original plastic to work with and a lot of hands-on experience to do this right. With a few years experience in handling these materials, at least it took me that long, one can learn how to fill tooth marks, and even reconstruct crystallized Doric Cathay Green cap and barrel ends! So you got a year or two on your hands to play around? If not send it to a pro like Old Griz suggests?

 

Syd

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BUT you have to have some scrap original plastic to work with and a lot of hands-on experience to do this right. With a few years experience in handling these materials, at least it took me that long, one can learn how to fill tooth marks, and even reconstruct crystallized Doric Cathay Green cap and barrel ends! So you got a year or two on your hands to play around? If not send it to a pro like Old Griz suggests?

 

Ain't that the truth? I spent the better part of 5 or 6 years learning the process, and developing my skills. I'm still making discoveries.

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  • 2 years later...

Sorry to uncover this long dead thread. I have a cheap fountain pen with a hairline crack along the barrel (starting from below the threads and spreading about 2/3 of the barrel length). I've read on various sites that using a proper solvent (like acetone) can fix this kind of damage...the reason I want to do this is I'm afraid the crack will spread to the threads and eventually split the barrel. Any kind of input is welcome. Thank you

Edited by dragos.mocanu

"The truth may be puzzling. It may take some work to grapple with. It may be counterintuitive. It may contradict deeply held prejudices. It may not be consonant with what we desperately want to be true. But our preferences do not determine what's true..." (Carl Sagan)

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Looks nice, but the shipping is 6.5 quid, more than twice the price of the product...I was actually thinking about a more household approach on this problem. I've read one can make such a plastic adhesive at home, using ground acrylic and acetone.

Edited by dragos.mocanu

"The truth may be puzzling. It may take some work to grapple with. It may be counterintuitive. It may contradict deeply held prejudices. It may not be consonant with what we desperately want to be true. But our preferences do not determine what's true..." (Carl Sagan)

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Looks nice, but the shipping is 6.5 quid, more than twice the price of the product...I was actually thinking about a more household approach on this problem. I've read one can make such a plastic adhesive at home, using ground acrylic and acetone.

 

 

What is your pen made from?

 

 

Different materials require different strategies (i.e. solvents).

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It's acrylic

"The truth may be puzzling. It may take some work to grapple with. It may be counterintuitive. It may contradict deeply held prejudices. It may not be consonant with what we desperately want to be true. But our preferences do not determine what's true..." (Carl Sagan)

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Looks nice, but the shipping is 6.5 quid, more than twice the price of the product...I was actually thinking about a more household approach on this problem. I've read one can make such a plastic adhesive at home, using ground acrylic and acetone.

Their local UK shipping is also expensive. See if you can find their products in Europe.

If you can't find any closer, I can always send some on to you if I can find a suitable small glass vial to put some into.

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Ok, so it's like this: I can't find any products named "Polyweld" on my local market, but there are a lot of products labeled "plastic adhesive" or "universal adhesive"(including plastic welding of course)..i guess that means some sort of super glue. What should the right sort of adhesive (or solvent) contain? I guess a local utilities shop should have what I need

Edited by dragos.mocanu

"The truth may be puzzling. It may take some work to grapple with. It may be counterintuitive. It may contradict deeply held prejudices. It may not be consonant with what we desperately want to be true. But our preferences do not determine what's true..." (Carl Sagan)

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Normal glues/epoxy don't really work too well on pens - unless you don't mind a big blob of epoxy on the pen.

You want to search for: plastic weld, plastic solvent weld or MEK.

There must be manufacturers in mainland Europe.

Try translating the terms into German and use google.de.

(MEK = methyl ethyl ketone, I think)

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I wonder if some sort of hobby adhesive for plastics would work. My intention is to apply it to the inside of the barrel

 

Edit: I've researched further and found out that Dichloromethane is a very efficient solvent for welding acrylic. Any opinions on that?...remember, the crack is small and very narrow, it may not need additional plastic cement (it should weld by itself)

Edited by dragos.mocanu

"The truth may be puzzling. It may take some work to grapple with. It may be counterintuitive. It may contradict deeply held prejudices. It may not be consonant with what we desperately want to be true. But our preferences do not determine what's true..." (Carl Sagan)

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  • 2 weeks later...

I wonder if some sort of hobby adhesive for plastics would work. My intention is to apply it to the inside of the barrel

 

Edit: I've researched further and found out that Dichloromethane is a very efficient solvent for welding acrylic. Any opinions on that?...remember, the crack is small and very narrow, it may not need additional plastic cement (it should weld by itself)

 

Hi dragos.mocanu,

 

First off, I'm newer than you to fountain pens so please do further research before even thinking about this idea that may or may not work on your acrylic pen:

 

I do, however, have experience with solvent welding (e.g. I fixed a crack in an acrylic aquarium) and plastic welding (using a soldering iron) on ABS motorcycle fairings and a car bumper). With the fairings and plastic car parts, I would spot weld along cracks in plastic to hold them together before using carbon-kevlar "soaked" in a 2-part epoxy glue to bond and strengthen the pieces (from the inside); something I don't think would be necessary to fix something like a cracked pen cap.

 

Pure acrylic (PMMA = polymethylmethacrylate) is a thermoplastic. Because of this, it can be heated to its melting point and cooled without changing its physical properties. HOWEVER, pure acrylic is clear and transparent. Parts of colored/translucent/opaque pens made of "acrylic" are probably not pure acrylic but acrylic mixed with resins, and other additives (e.g. thickening agents, etc.). I'm not sure how the physical properties of (pure) acrylic change with different additives. Parts of acrylic pens may also be coated with other materials. You'd probably have to go about figuring out what happens to the material empirically (i.e. trial and error method).

 

I'm just suggesting an alternative way to fix a crack on a thermoplastic material is by welding along the crack (from the inside) with heat. I've never tried this with a pen but it may work. The advantage is that you can adjust the heat carefully and have more time to work with. Fixing plastic with solvents doesn't give you a lot of time.

 

To fix a small crack in a pen cap, you might think about using heat from a fine-tipped soldering iron, carefully test it on the inside of the cap or barrel. If it feels like it's working, you could carefully slide the hot tip of the soldering iron inside the cap along the crack while squeezing the cap together with your fingers. If you do this, you should maintain pressure on the cap (pushing the edges of the crack into each other after you remove the heat to allow the melted plastic to set. The outside of the crack might then be melted and wet-sanded with 2500 grit (P-2500) wet/dry sandpaper to smooth it out, then polish it fine lapping sheets (e.g. 3M microfinishing lapping) for a glossy finish.

 

Once again, this is just an idea that I think *might* work if you do it carefully.

 

Aiden

the fantasy of inviolacy

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  • 1 year later...

This is all really great info. Thanks so much everyone. Going to go buy some acetone and MEK to try on a few pens that shattered as I was trying to take them apart. Excellent!

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