Experiment With Celluloid/mek

[siamackz]

This is my first attempt at using celluloid with MEK on cosmetic damage to pens. I took celluloid shavings mixed with MEK and tried to fill a deep hole and a scratch. After filling them, I let the celluloid slurry cure for about an hour after which I used micro mesh to buff it. The only issue is the pitting from the celluloid slurry. See pics of before and after. What am I doing wrong?

[fountainbel]

The liquid celluloid/mek mixture contains to much enclosed air bubbles

Viscosity of the mixture is probably too high and/or you should allow the mixture to "age" for a day, so the air bubbles can escape .

I expect the barrel is celluloid ?

In this case I'm surprised you did not use a simple celluloid/acetone mixture,

This work perfectly, so why use Mek?

Francis

[PaulS]

the bubble are created by the process of stirring the mix. Showing my ignorance, but if the mix is allowed to stand for a day, won't that defeat the requirement that it remains fluid when needed - i.e. harden long before the bubbles can escape ? Haven't I seen a suggestion of something called Devcon Two Ton Adhesive that dries clear, and which can be used on black bases?

Edited November 22, 2018 by PaulS

[siamackz]

The liquid celluloid/mek mixture contains to much enclosed air bubbles

Viscosity of the mixture is probably too high and/or you should allow the mixture to "age" for a day, so the air bubbles can escape .

I expect the barrel is celluloid ?

In this case I'm surprised you did not use a simple celluloid/acetone mixture,

This work perfectly, so why use Mek?

Francis

I Francis, I keep reading about how MEK is superior to acetone. Thats why I used MEK. But based on your advice I will try

(1) acetone

(2) let it be more liquidy when I pour it on. When I put the MEK its quite liquidy, I can see the MEK translucent. Once the mix is thicker and no trace of translucent is apparent then I poured it on. Is there a visual cue determin when the mixture is the correct viscosity to pour out?

Thanks for your guidance always!

Edited November 23, 2018 by siamackz

[Ron Z]

The advantage of MEK over acetone is that MEK penetrates more and evaporates at a slower rate. The evaporation rate of the solvent is what causes the bubbles to form. You can disagree with my chemistry professor friend if you like, but that is the simple explanation that he gave me.

 

Not all celluloids will respond to solvents the same way, even within the same brand and color. Some will tend to produce bubbles, some not.

[EdwardSouthgate]

Looks a lot better than it did .

[Honeybadgers]

If you plan on using epoxy for filling purposes, I recommend getting a small vacuum chamber setup, this is a quick and effective way to de-bubble epoxy.

[bass1193]

If you plan on using epoxy for filling purposes, I recommend getting a small vacuum chamber setup, this is a quick and effective way to de-bubble epoxy.

This all the way! Getting the dissolved gasses and gas by-products of curing out of the material before it cures is the best way to go. This can even be cheap, for something as small as fountain pens! Some fittings from a hardware store, some rubber, and a pot are all you need, other than a vacuum pump. That can be an expensive mechanical unit or even just a cheap hand-actuated one intended for brake bleeding

[Honeybadgers]

You could have a vacuum setup for under $50 even with a pump.

[bass1193]

You could have a vacuum setup for under $50 even with a pump.

 

Oooohhh where do you find such cheap vacuum pumps? Everywhere I've looked they're at least a Benjamin.

[Ron Z]

You could have a vacuum setup for under $50 even with a pump.

 

Not good ones. I've used vacuum chambers for several years, for various applications. The cheap ones pull down a vacuum, enough for bubbles to come to the surface, but not enough for them to burst. Even a very small leak can keep the vacuum from getting down low enough to be effective. I haven't had much success in getting the bubbles out of celluloid repairs, but maybe I need to revisit that with the better setup I now have.

 

A word of caution. The vacuum pump exhaust will contain vaporized pump oil. You really should use a muffler/oil trap so that you are not breathing the vaporized oil. A lot more comes out than you expect when running the pump, especially as it begins to pull the vacuum.

[siamackz]

If I dont have a vacuum though, what are some tricks to get the bubbles out? Should I stir the celluloid mixture less? Should I put on layer after layer after drying and then sand it?

[Honeybadgers]

don't stir it less - you need as much mixture as possible - less vigorous stirring may help, but if you REALLY want those bubbles out, get a mason jar, a hand vacuum pump, and use that. You can easily make a vacuum chamber for only a few dollars.

[fountainbel]

If I dont have a vacuum though, what are some tricks to get the bubbles out? Should I stir the celluloid mixture less? Should I put on layer after layer after drying and then sand it?

 

Sia,

Make your celluloid mixture less viscous and mix well.

Let the mixture age in a closed container overnight allowing the bubbles to escape.

Filling burning marks - as on your pen - I simply dip a 2 mm cylindrical steel pin in the liquid and let a drop of the liquid fall on the damaged spot.

Note the pin should not contact the part.

Apply sparingly and let dry for at least 24 hours

Dipping a small brush to apply the liquid one risks air bubbles enclosure between the brush hairs which are then transmitted on the part.

Using a less viscous mixture logically implies the need to apply more layers.

Wishing you success !

Francis

[siamackz]

 

Sia,

Make your celluloid mixture less viscous and mix well.

Let the mixture age in a closed container overnight allowing the bubbles to escape.

Filling burning marks - as on your pen - I simply dip a 2 mm cylindrical steel pin in the liquid and let a drop of the liquid fall on the damaged spot.

Note the pin should not contact the part.

Apply sparingly and let dry for at least 24 hours

Dipping a small brush to apply the liquid one risks air bubbles enclosure between the brush hairs which are then transmitted on the part.

Using a less viscous mixture logically implies the need to apply more layers.

Wishing you success !

Francis

Got it, thanks Francis!

[challer61]

If you plan on using epoxy for filling purposes, I recommend getting a small vacuum chamber setup, this is a quick and effective way to de-bubble epoxy.

 

This. It's only way to avoid entrained air. A hand pumped vacuum would be good enough.

[siamackz]

Are you guys talking about something like this https://m.youtube.com/watch?v=5Uc_xWgl1ZI

 

And how necessary is it really?

[Ron Z]

It is necessary in some cases. I can see where it would be useful in this application. Based on experience though, I don't know that a hand pump would be effective. While the video is nice, it doesn't show you how much vacuum it pulls.

 

I use a vacuum pump for a number of applications, and in some cases you must use one to degas the material or you get micro bubbles throughout. I would have to look up the data again, but the vacuum has to be pretty low to really be effective. I have seen cases where the vacuum goes low enough for bubbles to form on the surface of the material, but the bubble doesn't pop, no matter how long the material is in the vacuum chamber. As soon as the vacuum is released, the bubble goes back into the material.

 

Get a better tank and pump that will pull a lower vacuum, and you can get nearly all of the gas out of material.

 

I don't know what the cure rate is of your epoxy, but I would go with one that has a long cure time so that you have time to pull the bubbles out of the repair.

[siamackz]

I don't know what the cure rate is of your epoxy, but I would go with one that has a long cure time so that you have time to pull the bubbles out of the repair.

In this particular case I am using celluloid and solvent, not epoxy. So the time at hand once the mixture is made is really quite low. Dont think a vacuum will be feasible here, will it?

[CS388]

I usually just sand down and recoat. And then do the same again. And again. And again, etc, until I get a smooth surface free of imperfections and bubble holes. It's (obviously) very time consuming - although the later layers tend to be very thin and cure much quicker than the initial fills. The end result can be almost an almost invisible repair, especially with coloured celluloid.

 

However, I must repeat that I am not a professional restorer and this work happens on my own pens.

 

Enjoy.