Deteriorating Finish - Help

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yovalmtp

Member
Joined
Oct 20, 2020
Messages
4
Location
Enterprise, AL
I am new to turning and have made about 30-40 pens so far. I noticed pitting on an acrylic pen I turned about a month ago. When I finished it, it had a glass like surface with no blemishes. Now there are little pits or dimples forming. Has anyone had this happen before? What causes it? How do I prevent it? How do I fix it? I am posting my finishing technique because I am also seeing deterioration in the CA finish on my wood pens (small dimples in some cases and larger voids in others) and believe that I am doing something wrong. All my supplies are from Penn State Industries.
1. Turn to shape.
2. Initial sanding:
Wood/CA:
a. Dry sand wood: 150/240/320/400/600 grit, lathe turning 2000 rpm then long wise with lathe off. Clean the wood with alcohol to remove fine dust.
b. Apply CA: Gluboost blue 3-4 coats, Gluboost orange 3-4 coats with lathe turning at 700 rpm using a foam strip as applicator. I use Gluboost accelerator after each coat and let set ~1 minute between coats. Let set overnight before sanding.
c. Dry CA sand with 600 grit paper to take out ridges, lathe turning 2000 rpm then long wise with lathe off.
Acrylic: Dry sand 600 grit paper, lathe turning 2000 rpm then long wise with lathe off.

5. Both CA and Acrylic: Wet sand with plastic finishing pads, 800/1500/2400/4000/12000 grit, lathe turning 900 rpm then long wise with lathe off.
6. Both CA and Acrylic: Apply One-Step plastic polish long wise with lathe off and with blue shop paper towel till clear, then buff with shop towel at 900 rpm. Do this step twice.
7. Both CA and Acrylic: Buff with 4" cotton wheel using the Acrylic Buffing Bar for the Acrylic Pen Buffing System.

I don't know if this helps any, but I store my pens in a portfolio with 1" elastic straps and noticed the strap texture embedded in my CA finish. I apologize for the long post and appreciate and feedback.

Lee
 

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jttheclockman

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Feb 22, 2005
Messages
14,806
Location
NJ, USA.
I can talk about a couple things and start at the bottom. Absolutey that is a problem with those elastic bands in portfolios causes indents. Especialy those thin elastic bands. I would avoid. Can not speak about the glubost stuff I never did and never will use it. Let someone else answer that one. Now to your method way toooooooooooooooo much work. If you have to start dry sanding with 150 grit on wood you better learn to use your tools better or sharpen them. Anything lower than 400 grit is a waste of time in my eyes. The skew is your friend. Learn to use it. Any finish and that includes CA needs to cure to harden. Just because it is dry to the touch does not mean it is cured. You place pens in carry case right after making you are asking for trouble in many different ways. Off gasing of CA can cause plating problems when enclosed in a tight area. Plus the curing problem.

Pitting in acrylic is a new one on me. If it is a cast blank it is possible the blank did not cure and when you worked it you heated it causing these problems. If it is a commercial blank that should never happen. Unless you had not seen them originally. Now a little talked about fact is that everyone's chemical makeup is different and some people have more acid in their bodies that when touching pens and writing with them can cause discoloration of platings and also break down finishes. To me the pitting is something you may not be picking up right away and more technique in finishing is needed. Good luck
 

egnald

Member
Joined
Jun 9, 2017
Messages
510
Location
Columbus, Nebraska, USA
Greetings from Nebraska - I may be off base here, however, elastic materials can cause a localized strain induced accelerated corrosion and pitting on several metal alloys. Perhaps something similar is happening on the plastics of your blank and the CA which is also a plastic material.

Another thought is related to the material of the elastic as some synthetic polymers that incorporate plasticizers are notorious for damaging other plastic materials - flexible fishing lures for example easily damage other plastics over time simply by contact.

It would seem odd though that something designed specifically for this purpose, a pen binder, would use materials that are unfriendly to the materials used for pens. In any case, I have been looking at the binders as a storage solution recently and your post has definitely made me start to re-think things.

Regards,
Dave
 

Herman

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Joined
Oct 3, 2020
Messages
37
Location
Brazil
Hello everyone, greetings from Brazil! I am also not one of the most experienced with pens, but finishes and acrylic pieces I think I can help. The previous comments are well founded and I would like to offer you a simple and practical solution.

For Acrylic, there is a process known as annealing, when the internal stresses in the material are removed. It is a simple heat treatment, you will need a small electric oven with reasonably accurate temperature control. Simply place your pieces inside the oven, set the control to 80o Celsius / 176 o Fahrenheit and hold for 1 hour. Turn off and let it cool naturally. Do not open the oven and do not remove the parts from there until the temperature is below 40o Celsius / 104 o Fahrenheit. With this treatment we have achieved an improvement in the material's resistance to cracks, scratches and premature aging. It is necessary to clean the parts with soap and water before placing them in the oven, removing oils, cutting fluids and other impurities that may chemically attack the surface.

For the CA, the problem seems to be an incomplete cure. The solution is similar, also a heat treatment. Just the temperature will be 60o Celsius / 140 o Fahrenheit for an hour too. This procedure serves to speed up the drying of paints, enamels, varnishes and epoxy based glues. It greatly improves the characteristics of the final product.

I hope you have good results. Take care with oven constrols. Test initially with few pieces...

Regards
 

1080Wayne

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Joined
Feb 5, 2006
Messages
2,948
Location
Brownfield, Alberta, Canada.
There was no need to apologise for the length of your post . It was a pleasant change from the more cryptic ones we often see .
The more details that are given , the better the answer you will get .

It is possible that the strap texture embedded itself in the wax if it was too thick , rather than in the CA . That said , I agree with John that those straps are generally bad news . Their pressure can certainly mark a soft wood , and Dave`s comment on plasticizers affecting some resins may also be relevant .

Be aware that `acrylic` is unfortunately used by some as a term for all plastics , which have very different properties . Herman`s annealing technique can have value in some cases . It would help if he could clarify that he was referring only to methyl methacrylate , or if he has used it on other plastics with success . Welcome to the forum , Herman .
 

ed4copies

Local Chapter Manager
Joined
Mar 25, 2005
Messages
24,040
Location
Racine, WI, USA.
Looking at the pattern on the pen, I can contribute with some certainty that the material is acrylic acetate.
I have never seen pitting develop after the pen is completed.
 

Herman

Member
Joined
Oct 3, 2020
Messages
37
Location
Brazil
There was no need to apologise for the length of your post . It was a pleasant change from the more cryptic ones we often see .
The more details that are given , the better the answer you will get .

It is possible that the strap texture embedded itself in the wax if it was too thick , rather than in the CA . That said , I agree with John that those straps are generally bad news . Their pressure can certainly mark a soft wood , and Dave`s comment on plasticizers affecting some resins may also be relevant .

Be aware that `acrylic` is unfortunately used by some as a term for all plastics , which have very different properties . Herman`s annealing technique can have value in some cases . It would help if he could clarify that he was referring only to methyl methacrylate , or if he has used it on other plastics with success . Welcome to the forum , Herman .

There was no need to apologise for the length of your post . It was a pleasant change from the more cryptic ones we often see .
The more details that are given , the better the answer you will get .

It is possible that the strap texture embedded itself in the wax if it was too thick , rather than in the CA . That said , I agree with John that those straps are generally bad news . Their pressure can certainly mark a soft wood , and Dave`s comment on plasticizers affecting some resins may also be relevant .

Be aware that `acrylic` is unfortunately used by some as a term for all plastics , which have very different properties . Herman`s annealing technique can have value in some cases . It would help if he could clarify that he was referring only to methyl methacrylate , or if he has used it on other plastics with success . Welcome to the forum , Herman .
Hi Wayne, sorry for my incomplete explanation. OK, sometimes acrylic is a popular and generic term used for different plastics. I was thinking about PMMA, polymethyl methacrylate, Lucite, real acrylic. Annealing is very important for technical parts made with acrylic to extend the useful life, in order to remove internal stresses and stabilize it. This is my previous professional experience. Metals, glass and polymers can also receive heat treatments, but the temperature / time / heating and cooling curve must be in accordance with the material's technical data.
 
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