Telescope Reviews: Re: Restoring and Repainting Classic Telescopes

While additional collimation tweaking could not be done thru further tube repair, the stellar image now looks ok and I believe I can tweak collimation a bit more thru remounting of the focuser.

The next step in the repair process is cosmetic repair of the tube prior to repainting. To do it right necessitates complete stripping of the tube externally. This can be done for the most part with a good paint remover such as Strypeeze. It may have to be applied several times. A single edge razor plate can be used to scrape off soft paint and once as much paint as possible is removed, any remaining paint can be sanded off. Follow instructions on the can of paint remover and do not do this inside. Try to avoid getting the stuff under your fingernails. If it gets on your skin it will begin to irritate after a half dozen seconds or so. Clean it off as soon as possible, but you will not "melt". Avoid the fumes and keep it away from pets. Don't do anything to really tick off the "significant other".

Once you have a bare tube, the next step is external tube repair if needed. I love to use a product called JP Weld. It is kind of an epoxy type liquid steel. When the resin and hardener are mixed, the white and black colors of the separate components mix to form a battleship gray paste which will cure completely in about 24 hours. For small little nicks and scratches in a tube surface, put just a little bit on the nick or scratch and then spread out, over and into the scratch or nick with a single edge blade pulled across the surface. A small repair like this will be virtually completely dry in under 6 hours and can then be sanded level with the surface of the tube. Remember that the less "extra" you put on the tube, the less "extra" you will have to sand off.

For larger dents, the process is basically the same, you just have to use more and it takes longer to cure. With larger repairs, you want to keep the JB Weld from running. Do that by keeping the area you are repairing level, so the product cannot easily run out of the repair. There may be a tendency to see small bubbles in the JB Weld when you are using more of it; pop these with a straight pin. The JB Weld will seek it's own level, filling in any holes. After the stuff is cured and sanded the next day, sanding may reveal a small hole as you sand down a bubble that has not popped; fill this in with a little more JB Weld until the repair meets your expectations. This stuff is strong and hard, it has been used to repair cracked transmission cases. It sands very well and it takes paint very well.

After the tube has been cosmetically prettied up, you should prime first using a good primer recommended for use with whatever paint you want to use. I would first sand the tube with about a 200 grit paper before priming. For painting a tube I will typically run a broom handle or rug pole thru the tube, suspending the pole in the center of the tube by packing balled up newspaper around it. The pole is suspended between two garbage cans or anything else that may work that will allow me to turn the tube with the pole after several passes of the spray paint. >>>>>>>>Spray - right to left, and immediately back over the same area going left to right, turn the tube slightly and repeat, overlapping slightly with each turn. Follow recommendations for the right distance. Keep the spray can agitated to avoid spitting paint. The paint may spit when the can is close to empty. Follow temperature recommendations for painting. Avoid windy days. Go for a glossy wet look, but avoid overpainting and creating runs. Only experience and mistakes will help you here. When it looks right, turn the tube to see if there are any areas where you perceive the primer shining thru, if so, spray those areas one last time. Stay with the tube about 10 minutes turning the pole, this will help you avoid runs. (Also avoid days when there is a lot of airborne stuff flying around, pollen, dust, etc. If your next door neighbor is cutting his yard, don't paint.)

The paint has to cure, and you want this to happen in a dust free safe place. I once left a tube suspended on it's pole between two lawn chairs. I went inside and while looking outside saw a crow land on the freshly painted tube. He felt it made a good perch. This ruined the paint job, I had to start all over again!

Find a place to suspend the tube in your "Man Cave" or hobby area. No sense in ticking off the wife, or having her try to move something and messing up the paint job or getting wet paint on her clothing.

To be safely handled by hand, paint takes awhile to completely cure. A lacquer (most automotive colors) can be safely handled and used in 24 hours or less. An enamel takes a lot longer. While an enamel may look cured and you can carefully handle a tube with direct contact, the paint is still not completely cured. A tube like this will scratch easily, just try it with your fingernail. Avoid putting an enamel painted tube in a cradle at this point, the felt in the cradle will leave marks in the paint.

How long does it take enamel to cure? Perhaps weeks to fully cure, maybe a bit longer. You can help it along on small parts such as finder tubes, and short focus refractors that are about 4" and smaller. Do this by letting the paint cure on it's own for about 24 hours. At that point you can make a suspension system for the tube using bent coat hangers, threaded rod, etc. so that you can hang the painted part in your oven for curing. The key is no painted surface should come in direct ocontact with another surface. Suspend in oven and bake for one hour at about 150 degrees. Have the oven vent on to pull moisture out of the oven. When the buzzer goes off, turn the oven off and open the door. Let the part stay in place until cool enough to handle. This process drives moisture out of the paint and cures it. It also tends to make a painted part look glossier in color and deeper. A part cured like this can be used right after curing.

Unfortunately large parts cannot be oven cured. A hair dryer can help, as can direct sunlight. If you can, just keep a tube off to the side, and let it cure by itself for the next month. Avoid the tendency to use such a tube too soon, patience has it's rewards.

Here is a photo of a JB Weld patched tube prior to sanding, priming and painting.

Barry Simon

Edited by BarrySimon615 (03/31/08 11:28 AM)

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