Solvent Weld

[pen lady]

I'm trying to seal a crack with MEK. Things are looking good, but how long should I leave it untouched and clamped before I can carry on with re-assembly please?

[austollie]

Hi pen lady,

 

The answer depends on a bunch of factors, e.g. what strain is the joint under and what you are bonding. MEK (methyl ethyl ketone) is great for solvent welding small polystyrene parts. If you're using clamps, then presumably the part is under strain. In that case, I'd let it sit for 24 hours. If the part is not under strain, an hour should do, before you can move onto the next step.

 

Most fountain pen plastic parts are made from ABS (not polystryrene). I would doubt that solvent glueing with MEK alone will achieve a successful bond with ABS. My only experience with solvent welding ABS is for plumbing purposes. There, acetone based products are used for solvent welding (typically one to soften and clean the plastic and another for bonding).

 

Good luck with your repair.

Edited October 12, 2019 by austollie

[pen lady]

Wow, that was quick, thanks. It's an old celluloid combination fountain pen/pencil and the crack is behind the pencil's nose-cone, so yes, there is a bit of strain on it I'd say. I'll leave it undisturbed for a while then. Photos if and when it's complete!

[austollie]

Hi pen lady,

 

I have no personal experience with gluing or solvent welding celluloid, but I'd definitely leave it clamped for 24 hours to give the part any hope of bonding. Without having seen the piece, if the crack needs filling, I'd be tempted to use an epoxy product.

 

Good luck (and I'd love to see photos of the successful repair).

 

Ollie

[siamackz]

iirc from earlier posts I have read, it is best left untouched for days if not weeks. But I could be mistaken.

[Ron Z]

iirc from earlier posts I have read, it is best left untouched for days if not weeks. But I could be mistaken.

 

You're not. It takes time for solvents to evaporate out of the material. Data I've seen on solvent welding of material indicates that the initial bond is fairly strong, but the repair continues to strengthen over a number of days to weeks.

 

Ollie - I would not use an epoxy. There simply isn't enough surface area/contact area for a good bond. It might fill, but it is obvious. I've found that solvent welding, done properly, can yield a strong repair.

[siamackz]

 

You're not. It takes time for solvents to evaporate out of the material. Data I've seen on solvent welding of material indicates that the initial bond is fairly strong, but the repair continues to strengthen over a number of days to weeks.

 

Ollie - I would not use an epoxy. There simply isn't enough surface area/contact area for a good bond. It might fill, but it is obvious. I've found that solvent welding, done properly, can yield a strong repair.

Will the MEK wick in there even if its micro cracks?

[awa54]

I'm going to hijack this one a bit, if that's OK?

 

I posted regarding 60s Pilot plastics and solvent welding, got no answers, but it seems a good assemblage of knowledge on a similar subject is present here...

 

Does anyone know what plastic Pilot used on those? And is there a consensus on what solvents are best for each family of plastics?

 

TIA!

Edited October 15, 2019 by awa54

[Ron Z]

In general you'll use either MEK/acetone, or a solvent containing methylene chloride. If one doesn't work, try the other.

 

Don't forget that any of this stuff is toxic, so use with appropriate cautions, and understanding the risks.

[Bibliophage]

It's also VERY easy to use too much solvent. Practice on some broken pieces that you don't care about.

 

Preferably outside, over a rag.

[pen lady]

Thanks for all the warnings. I keep the MEK well away from my face and use a small paint-brush to apply it. In this case, the crack has sealed but because I didn't try to remove the metal sleeve first, it has closed but there's a grove where I was unable to clamp the sides fully shut.

 

Referring to Mr. Binder's site, I learned that Pioneer was a Wearever sub-brand, and at some stage the original nib has been replaced with a Warranted 14 K one. This is one of the items I'll have on my table at Scriptus - see you soon pen-people!

[austollie]

Hi pen lady,

 

That's a pretty impressive repair. Not bad at all.

 

Cheers,

 

Ollie

[Addertooth]

I would like to "TACK" this onto this thread on Solvent welding.

 

Cracks which are fresh, and don't have missing microfragments weld best.

Before you start compressing the part, which closes the crack, MARK the crack (somewhere where it will not be seen in the assembled pen) with a marker, such as a sharpie.

Marking before compression is done because, if you compress properly, the crack will disappear.... and you won't know where to apply the MEK.

Keep in mind that virtually all marker's lines are soluble in MEK, Position the crack facing up, so, should the mark wash away, you still know where the crack is/was.

I used a Q-Tip, with the cotton fluff removed to paint MEK on the cracked area in my example.

WAXED dental floss is a great material to compress a cracked barrel. You pull the floss tight as you wrap it around the cracked area. Add successive wraps of waxed floss until enough pressure is applied to the cracked part, so that the crack fully closes. You want ZERO gap. Keep in mind that each revolution of the wrap, which is pulled tight, applies force to squeeze the crack closed, more wraps equals more pressure.

It is a very gentle way to progressively apply pressure with little risk to the part you are trying to repair. The WAX coating on the floss, makes it easier to remove after the weld has cured.

Included below are pictures of the solvent repair in progress. It will sit on a marble block for about two weeks to cure. I am in no rush, ultimate strength is important as it is a high stress area on a Waterman Ink-View pen. It is the part which acts as the reservoir for the ink, and where the section screws in.

 

 

Edited November 4, 2019 by Addertooth

[FarmBoy]

I’d think one would want the crack and surrounding material to be as clean as possible and putting Sharpie on the part is asking for a stain.

[Addertooth]

I haven't had a problem with staining. The sharpie does not penetrate when I have used it. The MEK obliterates it. The body will get a polish after the weld, which would get rid of the rest of the traces.

The actual registration mark is a dot, and not along the entire crack.

But I suppose a piece of scotch tape, far away from the crack could be used to point to the crack. It would have to be far enough away that you won't get MEK on the scotch tape.

Edited November 4, 2019 by Addertooth

[txomsy]

Great advice. Please go on, I'm learning a lot.

[Addertooth]

Txomsy,

I don't mean to offend, some of the people here are very advanced. Some have never tried a certain type of repair. Often, what gets left out of some of the repair articles, is the simple stuff which is useful to those who have not done it before.

Edited November 4, 2019 by Addertooth

[txomsy]

Thanks, I totally agree. Which is why I am enjoying this thread so much.

 

Wish I had had this information forty years ago.

Edited November 4, 2019 by txomsy

[Ron Z]

Why do you need to mark the crack before applying MEK?? You don't close the crack and then apply the solvent, you apply the solvent and then close the crack. The solvent has to wet the walls of the crack to be effective, given a bit of time to soften the material, applied again and then the crack closed. A simpler way to hold it closed is with a dental band clamp, or Scotch 33+ electrical tape. It can be stretched when you wrap it around the barrel or cap, and will pull tight.

 

BTW, I agree with Todd - using a marker can stain the repair area. I make a concerted effort to remove all contaminants from the area before applying any solvent because once imbedded in the repair, you will not get it out.

[tmenyc]

100% agree with Ron about using the dental clamp. For longer cracks I"ve used two at a time. They provide even pressure around a circle. I tried to overtighten a junk pen some time ago to see what it would take to crush the pen, and the metal band snapped first, long after the "has to be too tight; you'd never crank it this tight..." thought.

And, a further thought about the marker: depending on the solvent used, old celluloid is such porous stuff that the solvent could even spread the marker pigment. If you need to have a visible mark, hold the pen semi-upright in a clothespin so that the crack is on top, then point your worklight directly down on it and the crack will be the most illuminated portion.

 

Tim