what is this "stuff"?

[Guest John Faulkner]

This is the old stuffing from my old AR-3s - my wife threw out the bag of "stuff" from one speaker, but I still have another bag/cabinet full. Is this the dreaded rock wool or fiberglass?

thanks

[Guest John Faulkner]

sorry, I forgot to post the picture!

[johnieo]

sorry, I forgot to post the picture!

John:

It does look like fiberglass -- uniform fiber texture -- not lumpy like rock wool. The yellow color we see in fiberglass is that of formaldehyde binder. It is possible that its color faded in 40 years or that a different binder was used. It does not have the overall torn chunky look of rock wool that was used for a few years when, I am told, fiberglass was in short supply. In any case, the question is academic as the original material is no more. Its replacement would be new fiberglass. Remove any paper backing and cut in about 4--6-in-square chunks outside the building using the normal precautions we have discussed many times.

Cheers,

John

[genek]

It does look like fiberglass -- uniform fiber texture -- not lumpy like rock wool. The yellow color we see in fiberglass is that of formaldehyde binder. It is possible that its color faded in 40 years or that a different binder was used. It does not have the overall torn chunky look of rock wool that was used for a few years when, I am told, fiberglass was in short supply. In any case, the question is academic as the original material is no more. Its replacement would be new fiberglass. Remove any paper backing and cut in about 4--6-in-square chunks outside the building using the normal precautions we have discussed many times.

If it is fiberglass, it wouldn't be original material. The yellow color of the old formaldehyde binder wouldn't fade that uniformly (I really don't think it would fade at all closed up in a dark cabinet). My guess is that this is either a finer grade of rock wool rather than the slag wool we usually see in old ARs, or someone's been in there before and has changed out the old stuffing for a newer, formaldehyde-free fiberglass.

Definitely toss this, whatever it is, and restuff both speakers with the correct amount of the same fiberglass.

[johnieo]

If it is fiberglass, it wouldn't be original material. The yellow color of the old formaldehyde binder wouldn't fade that uniformly (I really don't think it would fade at all closed up in a dark cabinet). My guess is that this is either a finer grade of rock wool rather than the slag wool we usually see in old ARs, or someone's been in there before and has changed out the old stuffing for a newer, formaldehyde-free fiberglass.

Definitely toss this, whatever it is, and restuff both speakers with the correct amount of the same fiberglass.

This has the same look as that of the fiberglass used in the "cut-away" version that Tom Tyson owns. I would submit that this is original material--fiberglass with a different binder.

John Faulkner: send me a piece about the size of a pea in a ziplok bag and I will put it under the SEM/EDX and tell you what it is for sure. I enjoy "academic" exercises such as this!

Cheers,

John

[genek]

This has the same look as that of the fiberglass used in the "cut-away" version that Tom Tyson owns. I would submit that this is original material--fiberglass with a different binder.

I did some checking, and it turns out that not all fiberglass production methods use chemical binders and that some grades of rock wool are combed to remove slag particles. So testing will be the only way to tell.