Chimney brick / mortar sealant?

Hi folks-
Had the local chimney sweeps out today. They did their routine inspection and came back with a few things "wrong" with the chimney that they could take care of me.
The one that I need help with is the brick/mortar sealant. According to the chimney guys, I've got some spalling going on, and the bricks and mortar need to be resealed. He cautioned against using "typical silicone sealants" because he says those trap some moisture inside the bricks, and when the chimney heats up, the trapped water can cause real damage. Instead, he said that the right product is a water based sealant that will repel new water but allow the moisture inside to breathe.
Something might have gotten messed up in the translation, but basically his point seems valid. The chimney is 35 years old, after all, and to the best of my knowledge, hasn't had any work done on it other than the occasional sweeping.
Any thoughts as to what products are available to DIY-er for this purpose? Looking for specific recommendations if possible.
Thanks in advance!
Marc
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<snip>

It seems that you resisted his call to sell you his particular brand of snake oil, that's good. Now further resist the urge to muck with your chimney. Good masonry does not need any sort of sealing, and if the masonry isn't good, then sealing will only prolong the inevitable a little bit.
That the chimney is 35 years old with no problems indicates that the masonry is sound. If things are finally deteriorating, find a good mason to do the work so that it will last at least another 35 years with out you having to do anything to it. If you've got spalling bricks you've got to find out what's causing that (likely the mortar needs to be repointed), fix that and whatever damage may have been done the right way.
John
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snipped-for-privacy@westnet.poe.com wrote:

Yeah, I would resist the expertise of a chimney sweep too. If MAG is worried, he should call a recommended mason to check his chimney.
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My Chimney was built over 12 years ago. The mason returned a couple of months later to apply a silicone sealant. My assessment is that it was worthwhile because today it looks just as it did when new. The cost for the sealant application was apparently part of his original very reasonable bid. No extra cost.
RB
MAG wrote:

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I would get a mason's opinion. Look for an ad that specifies that he does repairs. Or call a big masonry contractor and ask who they use to fix mistakes or point big jobs up. That is the guy you want looking at your chimney.

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snipped-for-privacy@mindspring.com says...

It's lasted 35 years, so I'm going to let it go until spring. When the weather warms, I'll go up there myself and see if the chimney guys was just "blowing smoke." If it looks like there is any real problem, I'll call in a mason and have it done right.
Thanks!
Marc
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