Adventures in Mirror Cleaning

The general advice on cleaning mirrors is don't. That is good advice. There comes a point where time, dusty wind, or a unsupervised child will force you to clean the mirrors.

This page specifically talks about my experience as a first time user using Collodion USP. This is sold in tubes by Mavidon. You can buy larger amounts for big projects. The web site gives very complete instructions on its use and safety.

Some Warnings that the Instructions Also Cover.

You are working with ether. It is explosive and toxic.
Work outside
Don't smoke.
Make sure nothing will cause static electricity

Case 1 - 8" Main Mirror

Dusty from travel
Need to preserve center ring
Glued into mount.

I created a dam around the full circumference of the mirror using masking tape. The picture above shows this partially in place. It is very important that the seal be tight. The Collodion is very thin and will leak if given a chance.

As the Collodion drys it will pull away from the surface. Don't rush this process. After a bit it will look like this

While this picture does not show it very well I did not put Collodion on the very center of the mirror. That way the center dot was preserved. This meant the very center was not cleaned, but the center is lost anyway to the shadow of the secondary.

The Collodion drys to a hard film. When it is completely dry it remove it with tweezers. Carefully blow off flakes or use a corner of some tape.

Quite a difference! I probably should have puffed the mirror since even in this short time it accumulated some dust. Note the contrast between the center which was not cleaned and the rest of the mirror.

Secondary

Unsupervised child
Travel dust
glued to spider

The secondary was a bit harder since you can not lay it flat. I clamped it to a miter box which made the surface level. I taped around the edges as best I could using 3M blue tape. The shape meant that on the right side above the tape was very close to the surface of the mirror.

During my first attempt at this mirror I rushed the drying process and / or did not shake the tube. The result was

That was discouraging. I tried cleaning the residue with some USP Isopropyl Alcohol. That helped, but did not remove everything.

Before Try 2 I shook the tube to mix the stuff. I pored it on rather thickly not by intent, but because the mirror was not initially clamped level. The stuff was allowed to dry for about 3 hours at 70º F (21º C). This time the dried Collodion came off cleanly. The result is not perfect, but way better than at the start.

Lessons Learned

Shake the tube
Allow very complete drying.

Is It Better Than using Water?

Good question. I have never used water to clean a mirror mostly because my optics are mounted using silicone glue.

What I can say

This is a fast method. Total time about 3 hours. Multiple Mirrors can be done in parallel
I bought the material in 2 Oz tubes. The two mirrors shown plus another secondary not shown required 2.5 tubes.
Allow time to dry completely
Shake the tubes
This method works with the optics mounted
It does not require you to touch the surface of the mirror
It makes short work of dust and fingerprints.

But I would still not make cleaning mirrors something I would do very often. I have a 15" mirror that is approaching the "when you see mouse tracks" stage. When it gets there I will use this method on it.