This blog post looks at plastic as an element in archival storage. It covers which plastics are archival and which ones are not. We’ll go over the pros and cons of using plastic in your archive. Then we will talk about the characteristics of the different types approved for storage.
Good Plastics / Bad Plastics for Storage
Good for Storage
Plastic is a synthetic material made from organic matter that is easily shaped during manufacturing. There are many types of plastics and we are going to look at the three that are generally accepted for archival storage use. Look for these three plastics and the “passed the PAT” stamp of approval. They should not be coated and not contain plasticizers or additives.
- Polyester
- Polyethylene
- Polypropylene
Bad for Storage
Do not use plastics labeled PVC, vinyl, or polyvinyl chloride in your archive. They off-gas and will harm your collections.
Polyester
Polyester, also known by brand names Melinex and Mylar, is the top choice plastic enclosure among many archives. It is the clearest, most inert, dimensionally stable, and rigid of the three approved plastics. Polyester has the highest melting point. It is also the most expensive of them. One drawback of polyester is that it can generate static electricity which attracts dust.
Our Polyester Products
- Polyester Side Loading Print Sleeves – 3 mil uncoated Melinex 516. One-piece construction with a flap-edge seal provides easy access and secure closure. Sleeves are slightly larger in both dimensions so that standard print sizes will fit properly. Please note that there is very little leeway on these sleeves regarding size. An 8 x 10 negative fits just right.
- Polyester Slide Lock Film Sleeves – same as above but sized for storing negatives and positives – 35mm, medium format, and 4×5 film (note: do not use plastic enclosures to store nitrate or older acetate safety film negatives)
- Film Interleaving Folders – same material as above, but a different design. These are only sealed along one short edge in 4×5 and 5×7 sizes. Recommended for use in conjunction with Open End Envelopes, inserting the open end of the folder first to protect against dust.
- 3-Ring Page Protectors – for use in 3-Ring Binders, these pages are the same material and design as the side loading print sleeves. The difference is they have 3-ring binder holes punched along the flap side and come with a buffered, acid-free paper insert in them. Available in two sizes – 9″ W x 11″ H and 10″ W x 11″ H. Both sizes will fit inside of our standard Collector Grade Binders and all of our Binder Boxes.
- Clear File Boxes – we sell these polyester boxes to store batches of 4 x 6 photos or postcards. You can include a reference photo on top or a piece of archival paper with notes about the contents of each box. Please note that they ship flat but are easy to assemble.
- Clear Print Mounting Strips – to add extra support when matting large prints
Polypropylene
Polypropylene, when in a sleeve format, is the next closest plastic to polyester when it comes to clarity and rigidity. It is also used to make Binder Pages, but for this use it is in a softer form.
Our Polypropylene Products
- 3 Sided Sleeves – open on one short side with no flap. Made of 1.5 mil Polypropylene, they have excellent clarity, low electrostatic charge, and are safe for long-term storage.
- Crystal Clear Archival Bags – same material as the 3-sided sleeves but they include a resealable flap for extra protection. The adhesive is on the bag rather than the flap, which reduces the chances of damaging your artwork when you are removing or inserting it.
- Polypropylene Slide Lock Film Sleeves – for storing negatives – 35mm, medium format, and 4×5 film (note: do not use plastic enclosures to store nitrate or older acetate safety film negatives)
- Print and Slide Pages – for use in 3-Ring Binders, these top-loading polypropylene pages come in many sizes. They are made of high clarity, archivally-safe polypropylene.
- Clear Mounting Corners – Mounting Corners are available in polypropylene. The high-quality pressure-sensitive adhesive does not come in contact with the document or photo being mounted. Available in several sizes in full and cut-back styles.
Polyethylene
Polyethylene bags are transparent but are not as clear as the polyester and polypropylene ones. It is a softer, more flexible plastic. High Density (HD) Polyethylene is cloudier than the standard polyethylene.
Our Polyethylene Products
- Polyethylene Bags – these poly bags are manufactured from uncoated, chemically inert 2 mil polyethylene. The 2 mil bags strike a balance between strength and clarity. All poly bags except the 3-1/2 x 5-1/2 size have a flap.
- HD Poly Envelopes – High Density Polyethylene Envelopes are semi-transparent with a frosted appearance. The anti-static qualities of the HDPE reduce the risk of scratching or abrasion from entrapped dust particles. HD polyethylene is one of the few plastic sheet materials with no slip agents added to the surface. Other polyethylene, polyester and polypropylene materials need slip agents to prevent the plastic from sticking to itself in rolls or sheets.
Plastic vs Paper
Now that you know about the different plastic storage options available, lets compare them to archival paper envelopes. Some archivists use plastic sleeves while others prefer archival interleaving paper and envelopes.
Plastic Enclosures
- clear so you can see contents easily which means less handling
- protects from oils and fingerprints during handling
- not easy to write on
- can trap gases and moisture
Paper Enclosures
- requires more handling to view the contents
- doesn’t protect from the oils on your hands which are damaging to photos, handle contents with gloves
- it breathes and protects from buildup of moisture and gases inside the enclosure
- protects from light
- easier to write on than plastic sleeves (only write on enclosures before inserting contents!)
- paper is better for the environment
Paper Binder Pages
We offer a binder page option for people who would prefer not to use plastic pages. We use archival, acid-free, buffered Card Stock to make 3-Hole Mounting Pages. They are available in white, gray, and black with the white being the heaviest weight paper (290 gsm), gray being the middle weight (210 gsm), and black being the thinnest (148 gsm).
They are available in three sizes – 10″W x 11″H for any of our standard binders, 9-1/2″W x 14″H for Legal Binders, and 8″W x 11″H for our Narrow Binders. These pages do not have any adhesive on them so you need to use something to attach your photos or memorabilia to the pages. We recommend a reversible product such as archival Photo Corners or E-Z Dots.
Related Products
The bags and sleeves are designed to hold many common sizes and will usually accommodate a backing board for added support. White Card Stock is a popular archival backing board as it is stiffer than paper but thinner and less expensive than 2-ply Matboard.
Available Sizes
Finding the proper sizes for your collection can be daunting. We’ve created this chart so you can see all the sleeve and bag options in one place: Size Chart for Plastic Sleeves & Bags. Here is the chart of Archival Paper Envelope Styles and Sizes.
