Are "acid-free" backing boards truly acid-free? Time to pH test & find out!

By M Schmidt

Discussions about the safety of various comic book storage supplies seem to crop up on this board relatively frequently, so I figured it was about time to put on the science googles and actually test a bunch of different backing boards in order to see which are truly archival-safe - and which, to put it nicely, don't quite live up their manufacturers' lofty claims.

Why is this important, you might ask? Well, as the paper in our beloved comic books ages, it generates a whole slew of deteriorative by-products/contaminants - most of which are highly acidic. The acids actually speed up paper degradation, so it's a rather vicious circle - as the acids build up within the paper, the production of new acids is greatly accelerated. If this build-up isn't stopped (or neutralized), the acids will eventually eat through the very molecular bonds that hold the paper fibers together - and all you'll be left with are brittle pages that turn to dust when handled.

Enter ... huzzah! ... archival storage solutions that slow down & impede this process.

In order for an item to be considered "safe for archival storage" (or "archival-safe"), it needs to be infused with a 3-5% alkaline buffer throughout (this buffer is typically calcium carbonate, CaCO3) which serves to absorb & neutralize the deteriorative by-products generated by the paper as it ages, and it also needs have an alkaline pH (eg. be acid-free).

Even though the terms "acid-free" and "archival-safe" are used interchangeably by the backing board manufacturers, they're not the same thing - acid-free means that your item was initially manufactured with a pH of 7 (neutral) or slightly above (alkaline). But as this does not guarantee that your item won't become acidic at a later date, a much more apt description would be "acid-free at time of manufacture".

For a much more in-depth explanation, check out this article on the Conservation Resources website:
Archival Papers

Anyway ... with that said, let's start testing to see which backing boards live up to these criteria.


Test specifics:

- Test were performed with a standard pHydrion pH pencil with distilled water.
- I used two different pH pencils - one pencil for the top line on each board, one pencil for the bottom line.
- All boards were cut in half, so I could test both the front & the back.
- All boards marked as "New" were taken from the middle of an unopened pack.
- Each test was allowed to sit for 15 seconds, then immediately scanned.

A small note about pH: 7 or thereabouts is neutral with everything below that considered acidic. The pH scale is a logarithmic progression based on the power of ten - so an item with a pH of 5 would be 10 times more acidic than an item with a pH of 6, and 100 times more acidic than an item with a pH of 7.


Items tested:

The description under each item is from either the manufacturers' website or their packaging.

Not shown in this photo - the Bill Cole Life-X-Tenders, the Bill Cole Thin-X-Tenders, and the BCW Extenders. Couldn't find the packaging for these, unfortunately.

1a) BCW's standard board (New)
1b) BCW's standard board (Used, 1 1/2 - 2 years old)
"24 point solid bleached sulfate"
"Coated on one side with a buffered with 3% calcium carbonate" (can't help but wonder if they jumbled up this description on purpose)
"Certified acid free - independent lab tested"

2) BCW's Extender (New)
"Will help prevent yellowing, retards the aging process, and absorbs and neutralizes the contaminants in comic book pages"
"Coated on 2 sides"
"Certified acid free - independent lab tested".

3) Ultra-Pro's standard board (New)
"Archival quality - acid free"
"24 point board stock, White, coated on one side"
"100% Archival Safe"

4) Hotflips' Comic Vision board (New)
"24 pt. board, coated one side"
"Archival quality" (on packaging)
"100% archival safe" (on website)
The old packaging for this board described it as being "acid-free" - this has been removed from the new packaging (as it should be).

5) Miller Hobby's standard board (New)
"24 point solid bleached sulfate, coated on one side"
"Acid free"
"Can be used for archival matting, mounting, and backing"

6a) E Gerber's Half-Back (New)
6b) E Gerber's Half-Back (Used, 1 1/2 - 2 years old)
"24 mil, acid-free, 3% buffered backing board"
"Meets strict U.S. Government standards for archival storage"
"3% calcium carbonate buffer throughout, maintains a neutral pH"

7) Bill Cole's Thin-X-Tender (New)
"24 mil thick acid free backing board"
"Archival quality protection"
"Impregnated with a calcium buffer resulting in an acid free, alkaline pH content of 8.5 throughout"

8) Bill Cole's Life-X-Tender (New)
"30 mil thick 3 layer board consisting of an activated charcoal layer (absorbs and neutralizes pollutants and by products of comic book paper) sandwiched between two acid free backing boards"

9) Old Board 2
Unknown age and unknown manufacturer.

Just for fun I also tested two pieces of Micro Chamber Paper - one was brand-new, and one has been sitting inside the front cover of the Megaton #3 CGC 9.2 shown in the picture above (as that was an old red label modern and CGC changed their labels back in 2003, that piece has been in use for at least 7-8 years).


Test images:

Everything was scanned on my trusty Epson Perfection 3200 with no corrections done in Photoshop. As I realize it might be hard to make out shades on a computer screen, I took the liberty of writing down the pH value that, to the best of my vision skills, corresponds to the colored strip on the board.


Test results:

As was to be expected, of the new boards every single coated backing board (BCW, Ultra-Pro, Miller Hobby and Comic Vision) failed the acid-free test - the coated/shiny side was in every case either pH neutral or pretty close to it, but this was offset by the heavy acidity of the uncoated side.

In contrast, every single buffered board (E Gerber and Bill Cole) passed the acid-free test - on these boards, both sides were pH neutral (or slightly alkaline), and as these boards are buffered throughout (not coated), the entire board can therefore be considered acid-free.

In regards to the used boards, the contrast between a coated & a buffered board is strikingly evident - whilst the 2-year old E Gerber half-back shows hardly any change in its surface pH, the shiny coating on the 2-year old BCW backing board has broken down & both the front and the back of the board is now acidic.

Even more telling is the measurements on the used "unknown board" - as you can see from the scan, the back of this board was heavily yellowed/tanned, and had a ghost-like impression from whichever comic book had been placed in front of it. Yet the pH values were very similar to the ones taken from the 2-year old BCW board which showed no external signs of degradation. As such, it's pretty safe to assume that just because a coated backing board isn't yellowed or nasty, doesn't mean that it isn't acidic.

One thing I found particularly interesting was the test of the Micro Chamber Paper (MCP) - even though the used piece had been absorbing the acids from a comic book for 7-8 years, the alkaline reserve in the paper hadn't diminished noticeably and there was no evidence that this paper was now "inert". This doesn't mean that the MCP will last forever - but it does show that CGC's estimate of a 7 year lifespan is probably on the rather conservative side.



The manufacturers/dealers who claim that their regular, coated-on-one-side backing boards are "acid-free", "archival quality", "archival-safe" or "acid-neutral" are either lying or misinformed.

These boards are all, at best, "acid-free on one side at time of manufacture" which tells you that at some point some part of this particular board was rendered acid-free, but that the rest of the board will happily contribute to the acidic environment inside your (sealed) comic book bag.

This does not mean that your comic book will spontaneously combust if it's put inside a bag with one of these boards - but it does mean, without a shadow of a doubt, that these boards will actively contribute, on a molecular level, to the decay of your comic book from the moment they're placed inside the bag.

As a matter of fact, it would be safer for your comic book to store them in a bag without a coated backing board.

Think of this way: if you treat just one side of a piece of wood with a water-proof sealer and then put the wood in a bucket of water, will the water not damage the wood? The water-proof sealer on the one side will certainly halt the destruction, but, ultimately, the water will thoroughly penetrate the wood.

So, in conclusion: The only true archival-safe (and acid-free) backing boards in this test are the buffered boards manufactured by E Gerber & Bill Cole.