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 Replies: 12 / Views: 7,935 |
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Valued Member
United States
307 Posts |
I am having a problem with toning and spotting of some of my collection. I am trying to find the cause and correct it. Mean while I have many graded coins in holders provided by the grader. Are these slabs air tight? The idea of the holder is to provide an environment to protect the coin. I don't know if they are air tight or not do you?
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Pillar of the Community
United States
737 Posts |
I don't believe they are completely airtight as they are gas permeable.
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Bedrock of the Community
Australia
21788 Posts |
I think the original intention of a slab was to protect the coin from physical damage, at the same time permanently including the grading notation with the coin. I don't think that air tightness or not was originally considered. So a commercial opportunity arises for TPG's, to introduce a 'new improved slab'! I understand some of the angst that arises when a beautiful rainbow toned silver coin starts to loose some of it's attractiveness within the slab after grading. |
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Pillar of the Community
United States
1388 Posts |
I think us collectors pay enough to grade our gems already... It should be airtight, but heat can affect it either way...
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Pillar of the Community
United States
6394 Posts |
Slabs are not airtight and susceptible coins (silver especially) will tarnish or tone inside the slab if it is exposed to, say, an atmosphere containing hydrogen sulfide and water vapor. You minimize this possibility by keeping the slab in a cool, dry container away from fumes, smoke, or other sources of contamination.
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Bedrock of the Community
United States
14454 Posts |
there are no slabs that I know of that are air tight. As a matter of fact there have been a few dealers that were fogging slabs and toning the coins inside them which would make everyone think the toning was Natural since they were in top TPG slabs |
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Pillar of the Community
 United States
2448 Posts |
What were they fogging them with? No, don't answer that; I'm sure someone would want to try it.
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Bedrock of the Community
United States
20753 Posts |
It is really difficult to make anything completely air tight. And that is even if that is the purpose done in a lab with really modern equipment. I highly doubt that a TPGS even considers making sure slabs are air tight. As already noted that is not the intention of a slab.
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Valued Member
 United States
307 Posts |
I realize you have to take additional precautions with all your coins to prevent them damage. I went to the safety deposit box and added gel packs to help prevent moisture even though the bank has a controlled environment.
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Pillar of the Community
United States
1745 Posts |
Slabs are generally ultrasonically welded and that operation does ensure an airtight seal. It some instances, it can be very water tight but not vapor proof.
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Valued Member
Canada
124 Posts |
It probably depends on the TPGS... Are your coins in PCGS slabs? I just read the following last week from PCGS' site ( http://www.pcgs.com/faq.chtml)Q: Can my coin change appearance after being placed in a PCGS holder? A: It is extremely unlikely that your coin will change appearance within a PCGS holder. The PCGS holder was designed specifically for the long-term storage and protection of your coins. The holder itself is made of inert materials that keep your coin safe. The sealed holder inhibits the entrance of atmospheric gases and contaminants that might harm your coin. Even so, common sense dictates that should keep your PCGS graded coins safe for a lifetime. Avoid humidity and excessive temperature swings by keeping your coins in a dry environment, preferably at a constant room temperature. If you have a coin that you think has changed in the holder, contact PCGS Customer Service and we can arrange to examine the coin for you. |
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Valued Member
United States
108 Posts |
Although the slab shells are sonic welded, the acrylic itself is gas permeable (albeit very low permeability). Thus, given enough time with the proper mixture of environmental gases, a slabbed coin will indeed tarnish. As referred to in a previous post, the original purpose of the slab was not necessarily to protect the coin from environmental hazards, so much as to physical hazards that can occur.
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Valued Member
United States
307 Posts |
The slabs happen to be NGC. However My question is concerning all slabs.
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Replies: 12 / Views: 7,935 |
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Posted 02/25/2011 12:43 am
