What is this plaster-like HVAC tape???

My HVAC unit is up in the attic. It works fine - I just cleaned the coils - but at each end, where the unit connects to the main intake and output ducts, it's wrapped with this plastery-looking material. It looks like strips of cloth that have been soaked in Plaster of Paris, or maybe wheat paste. Some of it has cracked and is leaking air, so I want to replace or add another layer to it. Can somebody tell me what this stuff is? Hopefully it's something I can buy cheaply at Home Depot.
Thanks, Ron M.
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Someone else here may know better than I, but that sounds exactly like asbestos. It used to be widely used as fireproof insulation for ductwork before it started killing people.
Leave the stuff alone unless you're absolutely sure that is NOT asbestos.
And if it IS asbestos, don't repair it. Either leave it alone or remove it properly (expensive).
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No, no, no. It's not asbestos. Not even close. This is where the main duct attaches to the central unit. It's just to attach it and seal it at the connection. It's a light cream/white color, and as I said, it looks like strips of cloth that were dipped in plaster of paris, then wrapped around the duct and allowed to dry.
Ron M.
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Sounds like mastic, which is just a thickened latex paint. Just gob over it with some fresh material from the big box store. Also consider using Mortite brand No Drip tape.
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IF you want something similar go to an autoparts store and look at muffler tape. There is a brand just as you describe , cloth tape with plaster of paris, that you soak in water and wrap around the exhust pipe to seal leaks

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snipped-for-privacy@rock.com wrote:

It is just duct sealant. You can get it at any HVAC supply. They may even have it at the Home Dope store.
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snipped-for-privacy@rock.com wrote:

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You are looking for duct sealant like CP 11 from Childers: http://www.industrialinsulation.com/images/vinyl_acrylic.pdf ______________________________ Keep the whole world singing . . . . DanG (remove the sevens) snipped-for-privacy@7cox.net

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