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How to ship sleek-free coated telescope mirrors

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#1 Cames

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Posted 14 January 2013 - 10:53 AM

How would I pack a pristine, coated primary mirror for shipping via commercial carrier cross-country? I dread the development of sleeks on the coated surface on the bumpy over-the-road trip and associated handling.

I’m pretty comfortable about creating the tight-fitting, firm, foam packing cut to the mirror’s dimensions with at least 2 inches of padding on all sides. The mirror should not be permitted to jiggle inside the packing.

The part I don’t understand is what I can safely place in direct contact with the meticulously cleaned coating in order to isolate it from the foam. Coated telescope mirrors seem to me to sleek with the slightest abrasion by any dry object.

Mirror coaters apparently do this successfully all the time. I’d like to know their secret.
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#2 Whoapiglet

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Posted 14 January 2013 - 11:06 AM

when I have had mirrors shipped to me they have come with the encapsulating foam (some use nerf balls cut in half) and the mirror was covered with either cotton balls or surgical cotton squares, covered by thick cardboard or particle board (pegboard type w/o the holes)cut tot he diameter of the mirror, which was then taped to the sides of the mirror so it can't shift in relation to the mirror surface.

I'm sure there are other ways but I never had any problems with sleeks or other damage this way.

#3 Bill Weir

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Posted 14 January 2013 - 11:21 AM

http://www.loptics.c...hop/shop21.html

It's how mine came.

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#4 FirstSight

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Posted 14 January 2013 - 11:29 AM

How would I pack a pristine, coated primary mirror for shipping via commercial carrier cross-country? I dread the development of sleeks on the coated surface on the bumpy over-the-road trip and associated handling.


Spectrum Coatings has excellent instructions for packing a telescope mirror for shipping. Scroll down on the page this link opens and you'll come to clear instructions, accompanied by photographs, describing how to do it using ordinary sturdy boxes and inexpensive materials available at any big-box hardware store, plus a sheet of optical-quality paper to go directly against the mirror. By "optical-quality" paper, I simply mean a type of paper that won't abrade the mirror by direct contact, not necessarily something you'd use to clean optics with.

I followed these instructions when I shipped my 12" mirror for a lengthy three-leg journey from Raleigh NC to Portland, Or for refiguring, from Portland, Or to Deltona, Florida for coating by Spectrum, and from Deltona, Florida back to Raleigh, NC. by ordinary ground UPS.

#5 GlennLeDrew

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Posted 14 January 2013 - 12:19 PM

A lintless tissue paper (resembling tracing paper) should be safe to place in contact with the optical surface. More than one layer is a good idea. Scotch or masking tape is advised to snugly wrap things so as to keep the tissue immobile. The tape need only be applied around the side of the mirror and/or the back side. On top of the tissue, which can be delicate, layers of other, more durable paper can then be wrapped (and snugged with tape, too, if desired.)

#6 okieav8r

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Posted 14 January 2013 - 12:30 PM

A lintless tissue paper (resembling tracing paper) should be safe to place in contact with the optical surface. More than one layer is a good idea. Scotch or masking tape is advised to snugly wrap things so as to keep the tissue immobile. The tape need only be applied around the side of the mirror and/or the back side. On top of the tissue, which can be delicate, layers of other, more durable paper can then be wrapped (and snugged with tape, too, if desired.)


I wonder if the kind of tissue that is used inside gift boxes would work? Seems to me it would be ideal.

#7 mark cowan

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Posted 14 January 2013 - 02:51 PM

No, absolutely not. It will attack the coating chemically.

Best,
Mark

#8 Mike Lockwood

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Posted 14 January 2013 - 03:12 PM

Bill posted a link above to my packing instructions.

Some important points:

1) Clean the mirror before packing.
2) Use acid-free paper if you care about the coating. It has no dyes, perfumes, etc. either. If it's going in for refiguring or recoating, it's not so important, but it is vital for bare glass or fresh coatings. Tape at the edge so it doesn't move.
3) Put cardboard over several layers of the paper. Tape at the edge so it doesn't move.
4) I recommend blue masking tape - it leaves much less residue than other tapes, and the coater will appreciate that.

#9 FirstSight

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Posted 14 January 2013 - 10:49 PM

Bill posted a link above to my packing instructions.


The fact that two high-quality professionals in the regular business of safely shipping telescope mirrors recommend virtually the identical procedure should assure you that this is indeed how it ought to be done. I do think Lockwood's added instructions on how to properly protect the mirror surface itself with acid-free paper are especially helpful for people wanting to preserve the existing coatings on mirrors. The Spectrum instructions are written with users in mind who will be shipping mirrors to Spectrum to strip the existing coatings off and recoat them, which is probably why those instructions didn't specifically address these additional details. HOWEVER, I'd note that when I received my freshly coated mirror from Spectrum, the surface was protected in precisely the manner described by Mike Lockwood - acid-free paper taped completely over the surface, then a layer of cardboard on top of that (with the foam layer over that).

#10 Cames

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Posted 15 January 2013 - 05:14 AM

I appreciate everyone's generous contributions. The scenario is clarifying for me now.

After your comments, I see how, in addition to abrasion, chemical interaction between the wrap and the mirror can also potentially degrade the surface. I had not thought of that.

Is the acid-free wrap used also known as the glassine type?
Where can relatively small quantities of the acid-free wrap be obtained?
Does the adhesive on the blue painters tape not penetrate the wrap? I assume taping should occur opposite the coated surface or at least be well-isolated from it.
Is there a concern that the surgical cotton may be acidic or be acid-processed? Its use among shippers appears to be more limited.

Edit: An afterthought - Has anyone experience with using a layer of the stretchy plastic cling wrap used in the kitchen (example: Saran wrap) in contact with coatings?
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C

#11 Patrik Iver

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Posted 15 January 2013 - 03:04 PM

Edit: An afterthought - Has anyone experience with using a layer of the stretchy plastic cling wrap used in the kitchen (example: Saran wrap) in contact with coatings?
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C


No personal experience of this, but my "local" workshop doing optical coatings, specifically warns customers not to use cling film "under any circumstances". They do not say why, but I guess there must be a good reason for the warning. I could provide a link, but the web page is in Finnish, so I don't think it would benefit that many CN'ers. :)

#12 Whoapiglet

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Posted 16 January 2013 - 11:59 AM

So is pure cotton bad? may not be ideal but will it damage? what if it is kept like that for a few months? (like my 8" zambuto that is awaiting completion of its new home?)

#13 ccaissie

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Posted 18 January 2013 - 11:10 AM

Clausing shipped my mirrors to me with a cardboard disk with cotton, like cotton ball stuff, under, against the coating. Worked well, and I still keep my reference sphere stored with this "lid".

C

#14 Mike Lockwood

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Posted 18 January 2013 - 10:41 PM

So is pure cotton bad? may not be ideal but will it damage? what if it is kept like that for a few months? (like my 8" zambuto that is awaiting completion of its new home?)

While it seems that cotton on a coating is fine for transport/shipping, I have seen some evidence over the years that leads me to believe that leaving it on for longer periods of time might cause coating degradation.

Possibly there is something in the cotton, or maybe it just trapped moisture near the mirror, or maybe it was just bad luck.

I'm not 100% certain. However, I generally use acid-free paper and haven't seen cases of degradation.

#15 okieav8r

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Posted 19 January 2013 - 05:07 PM

What is a good source of acid-free paper?

#16 Bill Weir

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Posted 19 January 2013 - 07:37 PM

What is a good source of acid-free paper?


http://www.ebay.com/...freetissuepaper

Or craft stores, printers etc...

Bill

#17 Mike Lockwood

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Posted 20 January 2013 - 12:27 AM

Try this for cost effectiveness:
http://www.papermart...=7782&SubGro...

#18 okieav8r

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Posted 20 January 2013 - 12:36 AM

Thanks Bill, Mike.

#19 JohnCK

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Posted 25 September 2013 - 12:08 PM

I recently received a 15” mirror as part of a purchase on Cloudy Nights and while the packing job was sufficient, the tape used was a major headache.
The mirror face was protected with acid free paper that was taped securely around the edge and back. The tape used was clear packing tape. When I pulled the tape off, the tape backing separated from the adhesive leaving the adhesive stuck to the edge and back of the mirror. It took a number of hours scraping with a razor along with solvents such as Goof Off to totally remove all the adhesive. I would recommend not using clear packing tape if it is going to be attached directly to the edge or back of your mirror. Further, I would recommend testing any tape you would stick to a mirror edge or back on plane plate glass to see how the tape will respond.

#20 Starman1

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Posted 25 September 2013 - 01:22 PM

The blue tape in the pics is also referred to as "painter's tape", and leaves virtually no residue.
If the entire mirror, front and back, is covered with acid-free paper, I wouldn't hesitate to use Gaffer's Tape, either. It's as sticky as duct tape, but leaves virtually no residue. I would not use it if the tape touches glass, however.

#21 Mirzam

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Posted 25 September 2013 - 02:50 PM

I had to send some mirrors back to Royce for rework and he recommended using Viva paper towels to cover the mirror front surface (Taped only on the towels not the glass). These are very soft and oil free towels and offer a ready alternative to optical paper.

Another experience involved a mirror purchased on Ebay as a blank. It was actually a finished mirror with a very nice figure--BUT there were weird marks and apparent gouges that appeared all over the surface as seen on the Foucault test. Dave Groski thought that these might be some sort of residue from wrapping the mirror in plastic cling wrap (he had a similar example). I tried acetone, alcohol, and battery acid in an effort to dissolve the residue. Nothing worked. Finally, I re-polished and re-figured the mirror at Delmarva and the surface eventually normalized.

Cling wrap is engineered to stick to glass. Don't ever let it touch the surface of a high precision optic.

JimC

#22 hottr6

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Posted 26 September 2013 - 09:59 AM

I had to send some mirrors back to Royce for rework and he recommended using Viva paper towels to cover the mirror front surface (Taped only on the towels not the glass). These are very soft and oil free towels and offer a ready alternative to optical paper.

I did this once, and placed corrugated cardboard over the paper towel. BAD MISTAKE! Do not use corrugated cardboard! During shipping, the coating picked up fine scratches that matched perfectly the corrugations in the cardboard.

The Viva paper towel was not an innocent player here. Maybe Royce has had good luck with Viva paper towels, but my one bad experience will ensure that I'll only ever use optical paper in the future.

#23 Mike Lockwood

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Posted 26 September 2013 - 03:21 PM

I had to send some mirrors back to Royce for rework and he recommended using Viva paper towels to cover the mirror front surface....

I did this once, and placed corrugated cardboard over the paper towel. BAD MISTAKE! Do not use corrugated cardboard! During shipping, the coating picked up fine scratches that matched perfectly the corrugations in the cardboard.
The Viva paper towel was not an innocent player here. Maybe Royce has had good luck with Viva paper towels, but my one bad experience will ensure that I'll only ever use optical paper in the future.

Agreed - only acid-free paper for me. That's what most coaters use, too. While other paper towels may not scratch, they may leave a residue on uncoated glass, and one may be surprised when the towel pattern reappears through the fresh coating.....

Surgical cotton is OK, but I have seen strange things happen to the coating if it is left on for long periods of time. This is likely because of trapped moisture reacting with the cotton.

We all put cardboard over the paper/cotton as a further protective layer, and I have not seen scratches from it, so I'm pretty sure the Viva was to blame there.






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