Spotting scope skin is tacky

[ChesterS]

It's called plasticizer migration. Plasticizer is used in some plastics, vinyl, rubber, and coatings to keep them flexible. Some coatings and all vinyls and rubbers continue to cure, shrinking and squeezing out the plasticizer. Plasticizers are often made from fatty acids are not very soluble in anything that most people have access to.
All of the double bonds aren't fully reacted when a product is made and continue react slowly over time. This is why rubber and vinyl and plastics become more brittle. UV creates free radicals and they help to open the double bonds causing this to happen more quickly. This can be slowed by adding uv inhibitors which either grab the free radical or absorb the energy. Just like sun tan lotion they eventually get used up. That's why you have to re apply suntan lotion. Newer coatings may now have the plasticizer attached somewhat to help reduce the migration. There was even work done to hand grenades to give them a soft grip so they don't slip out of a sweaty hand. (30 years in coating research)
P.S. My Kowa is in Japan being re-coated.

 

[bhoges]

There are several brands that are having this issue. Browning has riflestocks that do this and Bushnell.

 

[Just Say Moe]

I had a cheap scope that did this. I masked off the important parts and spray painted it flat black.

 

[QStott]

My Kowa 82 did the same thing. I stripped mine as well. It’s been a few years. I probably used brake cleaner or acetone. I left it black also. I had a green cover on it anyway.

 

[mikecockcroft]

My Steiner binos and Primos shooting sticks did it too. The Steiners got actual mussy spots and the Primos grip is so nasty that you cant us it. Both from being left in my jeep in the summer texas heat.

 

[FNSafari]

There are several brands that are having this issue. Browning has riflestocks that do this and Bushnell.

Oh God, another salt wood like episode for Browning ?

 

[DGP4]

I have had success with some items using acetone. Certainly worth a try if you have some on hand.

 

[centershot]

My camera lenses did that. I sold the camera. Problem solved.

 

[rijndael]

I have had success with some items using acetone. Certainly worth a try if you have some on hand.

I've used non-chlorinated brake cleaner with success as well. I rubbed it on with a low-lint cloth. The outer layer gets a little 'melty' and once the brake cleaner evaporates things re-harden a bit.

 

[STORM2]

I once had a device that developed that tacky outer surface. I can’t remember what it was however I do remember the fix. Talc or Q-stick chalk. Sprinkle it on, rub it in, wipe/dust it off. The thin coating left behind will bond with the surface and make you smile.