Protecting Copper Coinage.

Easier said then done ! I would say all known holders would not keep a red copper coin blazing red for a great length of time .So until they come up with a holder that is 100% safe for red copper , just keep them air tight as possible in a safe environment free of heat, humidity and very cold temps .

GENIUS!

When storing my valuable PCGS and NGC slabbed silver and copper coins, I use several products and precautions. First I will clean the slab using rubbing alcohol and makeup removing cotton rounds to remove dirt and debris off the slab. Let it dry and polish it with a micro fiber cloth. Next comes the Guardhouse Resealable Shield Sleeves made for coin slabs. This gives an extra layer of protection and deters scratches from occurring on the slab. Then it goes into the individual Intercept Slab Holder's and then into the 10 count Intercept Shield Box. Also In my coin safe I use Dry & Dry Brand Silica Gel Desiccant packs and put a few new shinny pennies and a generic silver bullion bar to act as the "sacrificial lambs". Any gasses, cooking smells, air fresheners, or Paraffin wax odor from candles that leak into the safe will attack these open Items before they get to the slabbed coins. If you dont have a safe, I would suggest a high quality Tupper-Ware Air tight container and use silica packs and a few sacrificial coins and bar. I've seen Red Proof Ultra Cameo Cent pieces turn to Red/Brown In PCGS and NGC Slabs, And Beautiful Blast White Walkers tone in holders. Regardless to what anyone say's, Coin Slabs from Third Party Grading Company's ARE NOT Air tight. Call me crazy, but I've spent too much time,effort,and money to see this happen to my graded coins.

@howell1018, you're correct, you can't rely on the TPG holder to provide the protection you need to prevent a red copper coin from turning, nor a silver coin from tarnishing. They are not air tight.

WalkerPF nicely outlined a list of protective measures; all those things basically come down to control of the humidity (and temperature) and protection from potential contaminants in the air.