Can you touch the tubes?

I avoid touching the print, lettering/numbers, info on old 1950s-1960s 9 pin signal tubes. The oil from fingers can smear the print on the glass.

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If you look through tube manuals under Installation and Application the only things stated are the socket pin counts and whether or not the tube can be mounted in any position. Since "touching the glass" is not stated (or "do not touch if they glow") you can assume it's something too obvious to print. 

Tubes do not get hot enough for the oils on your fingers to effect them.

This partially stems from the halogen lamp (and others) days as those things get white hot. 

Hello Emerging Soul!  The idea comes from the era when quartz mini bulbs (which run very hot) were introduced. Often found in desk lamps, the tiny bulbs almost instantly heat up to way past boiling water temperatures. Fingerprints leave oil on the surface. It takes time for the oil to heat up and that part of the "bulb" will heat up slower than the rest of the lamp. As all the bulb is trying to expand (slightly) as it heats, the slower heating parts will cause such a stress that the bulb may shatterl It will happen very quickly and the users hand will be in the vicinity as very sharp, very hot fragments of "quartz" will be sprayed about. This is a real problem with projector bulbs. I have replaced many such bulbs without problems, but I always leave them in the plastic bags they come in (after cuting off the bottom of the bag) when inserting them. Then, I just slip the bag off the bulb before applying power. Ordinary vacuum tubes are glass "bottles" that don't run nearly as hot and heat up gradually. Cleanliness and care are always a good idea, however.

Transistors was just coming into television sets when I started into electronics.  The only time we did not grab a tube with our bare finger was when it was hot.  We then used a cloth, napkin, paper towel...

Couple funny story now.  Wasn't then.

There were two tubes in the high voltage section in a tv that were in a metal cage/s.  The Regulator tube sometimes had a gripper or holder at the base.  We had to push down on the gripper to remove the tube.  You could only get one hand into the cage.  I remove the tube's anode cap.  Reach in, push down on the grippers with fingers and wiggle the tube up and out.  There is a point where the tube pins become exposed but are still connected.  I think it was a Zenith.  The picture tube anode was connected to the cathode of the regulator.  My fingers took one for the cause.  Yes, I did discharge the picture tube.  But the voltage creeps back.  On the larger 25, 27 inch tubes, they creep back with a vengeance.

The post above mentioned Halogen lamps.  Well, I got into Copy Machines after tv repair. They used to use Halogen lamps.  About 1/4 inch round, 12" long.    950 to 1250 watts. They fail in two ways.  Filament breaks, not light.  Or they get air in them, blackening the inside of the bulb.  e.g., get light but not enough = dark copies.  I could get to that lamp in a minute. Well, the lamp goes 1000 degrees in a second.  Takes about 5 minutes to cool down to touch.   Melting skin is like grease on that glass tube.