Lengthwise Shrinkage of Acrylic Acetate Blank Over Time

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magpens

magpens

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Early in my pen-making career (5 years ago), I turned some barrels from what I think is acrylic acetate. It's not the nicest stuff to work with but I know I did a good job and was very happy with the results at the time.

Today, I examined some of those "old" pens and discovered that the brass tubes on a few of them are protruding beyond the acetate blank ends by a small amount (estimated to be 10-15 thou; enough to notice) at both ends. The result is that the acetate no longer butts up snugly against the hardware components (eg. nib, coupler, centerband, etc.) - gap is visible.

The pen kits I have observed this phenomenon on are cigars and slimlines.

I don't think the brass tubes have expanded lengthwise :rolleyes: !

So I am concluding that the blanks have shrunk :mad: !

Yes, I am pretty confident that I glued securely with 2-part epoxy.

Just wondering if anyone else has noticed a similar effect and/or has an alternative explanation for this weird phenomenon.

If blank shrinkage is the correct explanation, then the epoxy glue would have had to do some "giving" or "creeping".

Comments appreciated.
 
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I have noticed this on a few very old El Grande pens. Seems prevalent on blanks that aren't left with much meat on them. I have other issues of fine fissure like cracks on the inside of AA blanks. Doesn't seem to matter how I drill them, what backfill paint or what glue I use. The cracks run lengthwise usually along the shiny section if the black has pearl in it. I haven't been able to suss this out so I don't do a lot of AA these day.
 
I don't remember the name of the thread, but I'm sure you can find it or someone else will, there was a thread not long ago maybe only a week or 2 on the same subject.
Curt
 
That's probably the same reason your dashboard cracks after a few years. The plasticizers evaporate and the plastic gets hard and shrinks. Same thing with your eyeglasses frames. My optician always warns me about possible frame breakage when I get new lenses. I like my frames, but they always add the disclaimer before working on them.
 
I thought this only happened in cold water? :)

I have some 5 year old AA and some PR that is 5 years. I have not seen it yet but I will watch for it. Does the same hold true for Glass that if you look at 100 year old glass panes you will see that the glass is actually still flowing. Maybe plastic behaves the same.
 
Pictures! We need pictures! - Sorry ... had to say it :)

Interesting - I wouldn't have thought it... I know I have my first wood pen, I don't remember if I saved my first resin one - I will have to go look to see what my oldest pens are and see if I can find that effect on any of them.

I am a little confused by the statement of "not the nicest stuff to work with". In my recollections of materials I've worked with, I thought the AA stuff (acrylic acetate) was some of the easier stuff. Inlace Acrylister - now thats a different story. Many have sworn of Inlace. Am I forgetting somethine about AA or is there something else I'm missing?
 
Never had a problem with (real) acrylic acetate. It turns well, threads well and polishes nicely. There are many plastics with acrylic or acetate in their name. Just saying.
Do a good turn daily!
Don
 
brownsfn2 said:
I thought this only happened in cold water? :)

I have some 5 year old AA and some PR that is 5 years. I have not seen it yet but I will watch for it. Does the same hold true for Glass that if you look at 100 year old glass panes you will see that the glass is actually still flowing. Maybe plastic behaves the same.
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I saw that in my old farmhouse. Windows that were older than dirt and they did show flowing. Loved it, gave the window just a little more authenticity when we told people it's age.
 
Ok, I guess this is not well known. Plastics as you likely are not aware of knows 4 conditions: HEAT, PRESSURE, FLOW & COOLING.

Plastic to can 'dry out' and subjected to any number of degrading factors over time.

Cracks can be used to determine what the problem was, you need to look at where and how the crack is forming.
 
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There are no cracks. I'll post some pictures in a few days ... just got a new camera which should be up to this job.

edstreet said:
Ok, I guess this is not well known. Plastics as you likely are not aware of knows 4 conditions: HEAT, PRESSURE, FLOW & COOLING.

Plastic to can 'dry out' and subjected to any number of degrading factors over time.

Cracks can be used to determine what the problem was, you need to look at where and how the crack is forming.
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This post is for you AlphaGeek and anyone else who is interested in actually seeing what I am talking about.

OK, here are pics of a couple of Sierra pens made 5 years ago. The blanks are Acrylic Acetate. One pen is chrome, the other is upgrade gold. The nib sections have been unscrewed a couple of turns so you can see the brass tubes protruding about 0.020" out of the acrylic in both pics. You also see the chrome (and gold) parts of the nib sections that have been unscrewed. It is the narrow brass tube piece on the right side of the gaps in both pics that I am concerned about. This brass has been exposed by shrinkage of the red acrylic.



.... Looks like my new camera and 100mm macro lens are up to this sort of work, and I am pleased about that. But I need to improve my skill at using them. I think the pictures need greater depth of field and I don't know how to get that; the F-number is already at its maximum and I moved the camera as far back from the subject as I could on the kitchen counter (and then enlarged and cropped the images with my editting software). Any suggestions ?
 
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AlphaGeek ... are you there ??

alphageek said:
Pictures! We need pictures! - Sorry ... had to say it :)

Interesting - I wouldn't have thought it... I know I have my first wood pen, I don't remember if I saved my first resin one - I will have to go look to see what my oldest pens are and see if I can find that effect on any of them.
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Trim it back and you will be OK. Do that by sanding or razor knife. Good for another 5 years. I can say I never had this happen and I have acrylic pens over 5 years old.
 
magpens said:
This post is for you AlphaGeek and anyone else who is interested in actually seeing what I am talking about.

OK, here are pics of a couple of Sierra pens made 5 years ago. The blanks are Acrylic Acetate. One pen is chrome, the other is upgrade gold. The nib sections have been unscrewed a couple of turns so you can see the brass tubes protruding about 0.020" out of the acrylic in both pics. You also see the chrome (and gold) parts of the nib sections that have been unscrewed. It is the narrow brass tube piece on the right side of the gaps in both pics that I am concerned about. This brass has been exposed by shrinkage of the red acrylic.



.... Looks like my new camera and 100mm macro lens are up to this sort of work, and I am pleased about that. But I need to improve my skill at using them. I think the pictures need greater depth of field and I don't know how to get that; the F-number is already at its maximum and I moved the camera as far back from the subject as I could on the kitchen counter (and then enlarged and cropped the images with my editting software). Any suggestions ?
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Question. Is it possible that the glue has broken down and the tube has slipped?
 
Without taking it apart just measure the blank and compare to a sierra tube length.:smile: Or just lay a tube next to the blank and you will know right away. That is why I get the big money Ed:biggrin:
 
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John,

You are absolutely correct, UNLESS you faced the tube and shortened the brass, when you made the pen.

BTW, GREAT picture, Mal!!!!!
 
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ed4copies said:
John,

You are absolutely correct, UNLESS you faced the tube and shortened the brass, when you made the pen.

BTW, GREAT picture, Mal!!!!!
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Wow went reaching for the stars on that one. :smile: If they did that then my first suggestion probably won't work because yes there is some leeway but not all that much. Will then run into refill length problems. May wind up doing a oops band aide.
 
A question that comes to mind (There I go, thinking again...danger, danger!:eek:), to try an evaluation to identify if this phenomenon occurred in a linear manner over 5 years, or was the dimensional variation (shrinking) concentrated early on. (A comparison we are well aware of is the changes that take place to a CA finish over the first few days or a week. After that initial period, the finish is fairly stable.) Perhaps when an acrylic blank is "fresh", it will shrink more, and then at some point in time it will find a relative point of stability. There is likely some relevant tech info available from the manufacturer of the product, but I do not know how to get that. It could be that if the acrylic shrinks more during it's first year of life as a pen blank, that the blanks and resultant pens would benefit from a practice of letting the 'age' for a year or so prior to use. Only a good analysis would establish the validity and value of doing that.

Mal, do you have some other finished pens of the same type material, of known age, to evaluate? That would provide a very rough analysis, but perhaps the combined experiences of many pen turners could ID the timeframe for the shrinkage to occur. I personally do not have aging finished pens of this material to evaluate.
 
Er .... wrong, Alphageek !! :biggrin::biggrin::biggrin:

I forgot to say that there is the same amount of shrinkage at the other end.


alphageek said:
magpens said:
AlphaGeek ... are you there ??
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My guess is that you will find the tube is pushed down and is missing that same amount at the other end! This looks more like movement than shrinkage. It's too uniform from what I can see.
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ed4copies said:
I would suggest taking that part of the pen apart and see what the other end looks like.
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jttheclockman said:
Without taking it apart just measure the blank and compare to a sierra tube length.:smile: Or just lay a tube next to the blank and you will know right away. That is why I get the big money Ed:biggrin:
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Already did that, Ed ........ other end looks the same

Already did that John ...... total length of acrylic is about 0.040" shorter than a Sierra tube .... NO !!! I didn't trim it too short in the beginning !!!! :biggrin:

I didn't think that a photo of the other end was necessary. I thought my credibility was such that .......... oh, never mind !!! :biggrin::biggrin::biggrin::biggrin::biggrin:
Read my OP.

I think it better just to post another picture or two .... showing both the nib end and the finial end.
 
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Measured length of brass tube = 2.424" ..... (Sierra click pen)

Measured length of the shrunken acrylic = 2.382"

Shrinkage of acyrlic = 2.424 - 2.382 = 0.042" ( or 0.021" at each end )

Certified by Magpens Bureau of Standards August 29, 2015 15:50 pm

Surely, I don't need to post further pictures. But go ahead and request 'em if you want 'em.

BTW, shrinkage is the same on both pens, the chrome one and the gold one.
 
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Very funny, Pete !! :rotfl:

Curly said:
5 years or so ago the Canadian dollar was worth more than it is now. The shrinkage is due to currency corrections. Soon the measured length of the acrylic will be about 1.680".
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Oh, I know that ... I was just joking :smile::smile: .... and thanks for your comment on my photos - would like to do better but that will come.
ed4copies said:
Not a question of credibility, Mal.

When confronted with a problem, best to check all the possible causes we can think of. No offense was meant.
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magpens said:
Er .... wrong, Alphageek !! :biggrin::biggrin::biggrin: I forgot to say that there is the same amount of shrinkage at the other end.
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huh... Well you've got me than.. I've never seen it and I'm still shocked that it's so "flat". I would think that it would warp or shrink non uniformly. But the item you've got is proof it happened... Weirdness.
 
I think I remember buying it from a local tool store in western Canada ... it was not from the "big names".

thewishman said:
I see what you are talking about. Do you remember from whom that acrylic was purchased? I have some pens almost twice that old that have not had any problems, with blanks from Berea and CSUSA.
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OK I think you have very good proof that it can happen. I have no explanation for you. The only one I could think of is if this was a custom pour then maybe the resin did not have long enough to cure before it was worked.

I will be honest and again say I have never seen this. First time for everything. I guess you just need to do a redo. Good luck and thanks for showing. By the way photos tell the story very well.
 
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