Do Full Red Coins Stay Red In A Slab?

Slabs aren't airtight. No, you cannot trust a Red copper to stay that way in a slab. It might; it might not.

Your call. I don't buy Red copper.

I totally agree with the above posts. I don't want to pay a premium for a red IHC that I can't guarantee will stay red. I much prefer the chocolate brown and browns with some red undertoning.

I usually stick with BN and RB copper. On some of the more inexpensive coins, I will be willing to go for RD coins. Like what others have said, copper can turn colors and acquire spots in the slab. I remember reading something about a certified 1963 PR-70 DCAM Lincoln that sold for, I think around $40,000. It eventually developed spots over the coin while in the slab and was eventually bought back by the grading service. The link below takes you to a Heritage lot where the coin is certified as being RD but the coin is not looking so RD anymore.
http://coins.ha.com/c/item.zx?saleN...2&lotNo=7332

I'm surprised to hear that the TPGs don't actually have airtight containers for copper. From the sound it of there is a little more to maintaining the red color than that (I was never a chemistry person), such as surface contaminants that may not show up for some time, but at least an airtight container would help a lot with keeping excess oxygen out.

The TPGs say that they use ultrasonic welding/sealing to encapsulate, why is this not airtight? I would think they could find a way to make it a complete seal.

I don't think it needs to be vacuum sealed or oxygen free, assuming the container is now air-tight. It's a finite and relatively small amount of oxygen that will get 'used up' as the copper reacts with it. Yes a very slight degree of color change will occur, but it would be very minor and still a lot better than having the container unsealed.

Forgetting the vacuum sealing part, it's shouldn't be expensive to completely seal the plastic air-tight. Ultrasonic welding just melts the plastic so I've gotta believe that its within the realm of possibilities with the equipment they're already using. If not, there are certainly other cost effective ways to do it.

Unsure just how long this has been in this but it is still red

Not in a slab but notice these look the same way they did in 1959 when I put them there. Proves that there is always a way to make sure a coin stays the way it was when new.

And someone did this and I purchased it a long, long time ago and it still looks new too.
It is odd that so many TPGS's say there slabs are safe from toning and are air tight. Yet so many end up toning anyway.

ICG offers an optional product called Intercept Shield (IS) that is used as the slab insert. This proprietary material supposedly protects the coin from tarnish, toning, and oxidation in general. I just called ICG and they report IS is not popular but they still provide it upon request, for a small extra charge. They do not guarantee it will preserve the original red luster on copper coins, however. For what it is worth, I have had two IS-slabbed silver coins in my collection for 6 and 10 years respectively and they show no changes in luster and color.

The IS material was also used to make boxes for slabs, either single-slab cases with a viewing window or larger boxes that hold about 20 standard-size slabs. These would add another layer of protection for slabbed coins in storage.

The IS technology may not be getting a fair shake in the marketplace due to their 2nd-tier status among grading services. If PCGS offered the product I think it would be more popular and we could likely get some expert opinions about whether, and how well, it protects RD copper.