Should I Replace Crystal Mounts Immediately?

I inherited a small collection from a relative - generally unused commemorative stamps from the 1940s to the 1960s that are mounted with Crystal Mounts. The collection also included a few packages of Crystal Mounts of various sizes.
Based on a couple of comments I have seen, my sense is that Crystal Mounts are considered inferior to other types of mounts (e.g., Showgard, and perhaps others). Sorry to have to ask, but why is this? And should stamps mounted with Crystal Mounts be remounted with other brands immediately?
Thanks in advance for your responses!

Inferior would be an understatement. Crystal mounts were more likely to damage stamps than protect them.

Thanks, JLLebert. Do you know how the stamps would be damaged? Damage the gum, change the color, or something else?
In any event I'll start replacing these mounts right away (and toss the bags of unused Crystal Mounts). I'm just trying to figure out if I need to do anything to these stamps during the remounting process.
Thanks!

They shrunk/squeezed the stamps

Not only did the Crystal mount plastic sometimes shrink, damaging stamps, but they could leak adhesive which threatend the stamps and nearly always badly damaged the album pages they were mounted on. On the other hand, in remounting a few pages of stamps that were in Crystal Mounts in my own collection recently, I found I was lucky that most of my Crystal Mounts had not succumbed to these problems, so it is possible that they won't damage stamps. It may have to do with how the albums are stored. Heat may activate the breakdown of the mounts.

I removed all those mounts and replaced them with modern black-backed mounts. Crystal Mounts are all clear so you can see the brown adhesive staining through them.

You often cannot just pull them off the page, but using a razor knife you can cut them open, remove the stamp and then slice the rest of the mount off the page, leaving a small part of the back of the old mount still attached to the page. Over that, I placed a new mount. Of course, with the Crystal Mount adhesive still there, who knows what might still happen, but these mounts were well over 50 years old, so I don't imagine their remnants will disintegrate. You'd be wise to remove all Crystal Mounts you come across. It takes little effort to do this.

I have several packs of Crystal Mounts I found in a box that have not shown any obvious deterioration. I do not use them but keep them as a curiosity item.

Anyone who is using them should replace them immediately. They do horrible damage to stamps. And just because you don't see any deterioration does not mean that it hasn't happened. You won't see shrinkage when they are still in the packaging.

YES!





Any or all plus compressing or staining the stamp.




Remounting will stop the deterioration, but any damage will remain.

DO NOT PULL (SLIDE) the stamp from the mount. First slice the mount open, usually at the bottom and then remove the stamp. Non-spade tongs work well.

Everything I've read about Crystal Mounts says "get rid of them", but in 1976 I got mint commemorative stamps from 1950 to 1976, and fit Crystal mounts to them.
I cut them to length, separated them by inserting a tong point into the seam and sliding it end to end, then refolded the mount to better fit the stamp, pressed the fold flat the end of the tongs.
Just looked thru the Scott Minuteman album all that stuff is in and don't see any damage. I'm sure thay are, but I can't see anything wrong. But my results are one of a very few lucky reports of the use of Crystal Mounts

Thanks for all the responses! I'll start replacing these mounts Crystal Mounts right away. It doesn't seem worth the risk to leave stamps in Crystal Mounts, and in my opinion the newer black background mounts look better anyway. Also, tanks for the tips about removing stamps from Crystal Mounts (slicing the mounts open first, rather than than trying to pull the stamps out before slicing the mounts).

As littleriverphil notes, occasionally someone hits the winning lottery numbers; otherwise enjoy the remounting.