Are slabbed coins vacuum sealed?

[Bimetallic]

Hi all – Do the NGC and PCGS vacuum seal their slabs? It's hard for me to tell from photos how much potential air volume there is in these slabs. Is it an issue at all? Do they nitrogen flush along with vacuum sealing? (I've seen that in some industries, like food packaging.)

[KevjustKev]

Looking at the ones I have, both NGC and PCGS, I can't see how they would or could. There is no 'output' nozzle, nipple or tip marks to suggest any vacuuming has been performed. That being said I'd say no. 

[HyHy]

No they aren’t both NGC and PCGS slabs are only sonically sealed and these plastic slabs are permeable means surrounding air can still diffuse into the slab.

[Bimetallic]

21 hours ago, HyHy said:

No they aren’t both NGC and PCGS slabs are only sonically sealed and these plastic slabs are permeable means surrounding air can still diffuse into the slab.

Really? Air can go through the plastic? Or is it just that the seals have leaks?

[HyHy]

17 minutes ago, Bimetallic said:

Really? Air can go through the plastic? Or is it just that the seals have leaks?

It's not about the seal, it's because plastic is porous to air and air would able to eventually diffuse through the material.

[Bimetallic]

8 minutes ago, HyHy said:

It's not about the seal, it's because plastic is porous to air and air would able to eventually diffuse through the material.

Wow, I had no idea. Is this true of plastic in general or just the polymer they use? People store all kinds of things in vacuum-sealed plastic bags, and it seems like it would be pointless if the plastic was permeable.

[PansPurse]

3 hours ago, Bimetallic said:

Wow, I had no idea. Is this true of plastic in general or just the polymer they use? People store all kinds of things in vacuum-sealed plastic bags, and it seems like it would be pointless if the plastic was permeable.

It depends a lot on the particular plastic, the macroscopic format (e.g. expanded polystyrene versus compressed polystyrene). This is a challenge that lots of food packaging manufacturers face. For example, coke bottles are deliberately over pressurised compared with cans because of the porosity of the plastic. Also different substances can permeate different plastics. Fun fact, firefighters, when investigating a fire, sometimes bag evidence in a nylon bag, then a polythene bag around the outside.

[Bimetallic]

It depends a lot on the particular plastic, the macroscopic format (e.g. expanded polystyrene versus compressed polystyrene). This is a challenge that lots of food packaging manufacturers face. For example, coke bottles are deliberately over pressurised compared with cans because of the porosity of the plastic. Also different substances can permeate different plastics. Fun fact, firefighters, when investigating a fire, sometimes bag evidence in a nylon bag, then a polythene bag around the outside.

Interesting, I've googled it and read a lot about how permeable plastic is – I really had no clue. (Amusingly, some of the search results are about getting pot past drug-sniffing dogs, and how they can smell through the plastic.)

What about the material used for coin capsules? What kind of plastic is it and how permeable? I've seen suppliers go out of their way to state that it's not PVC, so I guess there are some issues with PVC and coins, but I don't know what that's about. But when they said there was no PVC, I don't remember them saying *what it was* instead.

[kimchi]

2 hours ago, Bimetallic said:

Interesting, I've googled it and read a lot about how permeable plastic is – I really had no clue. (Amusingly, some of the search results are about getting pot past drug-sniffing dogs, and how they can smell through the plastic.)

What about the material used for coin capsules? What kind of plastic is it and how permeable? I've seen suppliers go out of their way to state that it's not PVC, so I guess there are some issues with PVC and coins, but I don't know what that's about. But when they said there was no PVC, I don't remember them saying *what it was* instead.

Good question. I also wonder how the cheap Chinese capsules compare to the 'big brands', I guess at least some are best avoided, but how to tell.

(Any good tips on the pot? )

[Bimetallic]

Just google 'is plastic permeable', without the quotes, and you'll see what I mean on the very first page of results, probably the third or fourth link.