Comic Encapsulation & Mylar Protection

Why Polyethylene Bags Aren’t Enough

Many collectors put their prized comics in polyethylene bags thinking, “this is a good enough preservation move,” only to find years later that the quality of their books has deteriorated.

While polyethylene bags are acceptable for short-term storage (months to a few years), they are not considered a safe long-term archival solution. Polypropylene is generally more stable, but polyester film encapsulation (BoPET) is considered the gold standard for long-term stability and value.

Understanding Plastic Types: Mylar® and Melinex®

Mylar® is a trademarked brand of polyester film (originally DuPont). While collectors often use the term generically, it refers to a specific biaxially-oriented polyethylene terephthalate (BoPET) film known for its high tensile strength and chemical stability.

Mylar Sleeves: The Logical Long-Term Storage Choice

Uncoated archival-quality polyester film encapsulation, commonly called “Mylar” sleeves, is the most logical form of long-term storage in direct contact with your comic books. Polyester is chemically inert and will not yellow or crack with age. These sleeves typically come in thicknesses ranging from 1 to 4 mils.

Archival Resources & Specifications:

Handling Notes:
  • Thicker Mylar (4 mil): Provides superior rigidity and support for fragile books but can be stiff and difficult to fold precisely.
  • Thinner Mylar (1–2 mil): Offers great clarity and flexibility but may be prone to creasing or tearing if handled roughly.

Professional Grading & Tamper-Evident Holders

Professional encapsulation, often called “slabbing,” uses advanced tamper-evident holders designed to protect the comic and preserve its assigned grade. These holders are sonically sealed; once closed, they cannot be opened without breaking the plastic, providing a clear “proof of entry” that protects the integrity of the grade for the secondary market. Although, lately tamper resistant is most ly a better term.

Grading Services:

  • CGC (Certified Guaranty Company): CGCcomics.com — The market leader with the most widely recognized grading slabs and generally higher resale values. CGC offers a robust grading scale and signature series but has faced some recent quality control and grading consistency concerns.
  • PSA (Professional Sports Authenticator): PSAcard.com — A newer entrant in comic grading, trusted in sports cards, with growing presence in comics. Not the cheapest option currently, but may offer the best sales prices if your selling highend vintage comics. Please do your own research.

Key Features of Modern Holders:

  • Sonic Sealing: High-frequency sound waves weld the two halves of the holder together, creating a permanent bond.
  • UV Protection: Many modern slabs incorporate UV-resistant additives to help prevent fading from light exposure.
  • Micro-Chamber Technology: Some services include specialized archival paper (Micro-Chamber paper) inside the holder to neutralize acids and pollutants.

Display & Secondary Protection

For collectors who display their books or want an extra layer of security for graded “slabs,” several specialty products are available:

  • Millcase: A hard plastic case with UV filtering. Millcase.com. Note these cases may not fit well in current situations, in terms of the use of Acid-Free Backing Boards or other items such as MicroChamber Interleaving Paper. Test before you buy large amounts of them.
  • Archival Envelopes: 10-point tan, acid/lignin-free buffered (pH 8.5) stock with a crystal clear polyester window. See-Thru Comic Browser/Storage Envelopes

Support Materials

MicroChamber Interleaving Paper

MicroChamber paper is a specialized, lignin- and sulfur-free archival material embedded with proprietary SPZ zeolites. These “molecular traps” actively absorb and neutralize acidic pollutants, oxidative gases, and the off-gassing associated with paper degradation.

Research & Resources:

Acid-Free Backing Boards

These stiff boards provide essential structural support to prevent bending, creases, and color breaks. High-quality archival boards are acid-free and typically include a 3% to 4% calcium carbonate buffer to maintain an alkaline pH (around 8.0), neutralizing acids over time.

References:

Resource Index