NGC Encapsulation & Conservation 2 — Questions and Answers
Question 1: What material is used to make NGC's tamper-evident coin holders (slabs)?
- Polycarbonate plastic (Correct answer)
- Acrylic glass
- PVC vinyl
- Polyethylene foam
Correct answer: Polycarbonate plastic
NGC slabs are made from inert polycarbonate plastic, which is chemically stable and does not off-gas harmful compounds onto coins.
Question 2: Which of the following is a primary reason NGC encapsulation is considered conservation-grade?
- The holder is airtight and uses inert materials (Correct answer)
- The holder is coated with UV-blocking paint
- The holder contains silica gel desiccant packets
- The holder is stored in refrigerated vaults
Correct answer: The holder is airtight and uses inert materials
NGC slabs use inert, non-reactive materials and a sealed environment to prevent atmospheric contaminants from reaching the coin's surface.
Question 3: When removing a coin from an NGC slab for re-examination, what is the correct first step?
- Score and crack the slab at the seam carefully (Correct answer)
- Soak the slab in acetone to dissolve adhesives
- Freeze the slab to make plastic brittle
- Pry the holder open from the label end
Correct answer: Score and crack the slab at the seam carefully
The accepted method is to carefully score and crack the polycarbonate slab along its seam to extract the coin without damage.
Question 4: What does the term 'environmental damage' refer to in NGC's grading context?
- Damage caused by exposure to chemicals, moisture, or improper storage (Correct answer)
- Damage caused by mishandling during shipping
- Scratches from improper cleaning
- Strike weaknesses from die wear
Correct answer: Damage caused by exposure to chemicals, moisture, or improper storage
Environmental damage in NGC's context refers specifically to coin surface degradation caused by exposure to chemicals, humidity, or reactive storage materials.
Question 5: Which conservation treatment does NGC consider acceptable before encapsulation?
- Removing loose surface debris with a soft brush (Correct answer)
- Dipping in commercial coin cleaner
- Buffing with cloth to restore luster
- Applying lacquer coating to prevent toning
Correct answer: Removing loose surface debris with a soft brush
Gently removing loose debris with a soft brush is acceptable conservation, while chemical dips, polishing, or coatings are considered alterations.
Question 6: What NGC designation indicates a coin has been cleaned or altered but is still genuine?
- Details grade (Correct answer)
- Proof designation
- Cameo designation
- Star designation
Correct answer: Details grade
NGC assigns a Details grade to genuine coins that have been cleaned, polished, or otherwise altered, describing the specific problem on the label.
Question 7: Why does NGC avoid using PVC-containing materials in its holders?
- PVC off-gasses chlorine compounds that cause green slime deposits on coins (Correct answer)
- PVC is too brittle for long-term storage
- PVC is more expensive than polycarbonate
- PVC blocks UV light needed for photography
Correct answer: PVC off-gasses chlorine compounds that cause green slime deposits on coins
PVC releases chlorine-based plasticizers over time, forming greenish residue on coin surfaces that is corrosive and extremely difficult to remove.
NGC Encapsulation & Conservation 2
What material is used to make NGC's tamper-evident coin holders (slabs)?