Very good for sealing ductwork.Would have been bet ter if the co mp any would have put Ta pe to keep l I d on during tra ns Port.

Absolutely thrilled with this purchase! The product exceeded my expectations in every way—great quality, well-made, and performs exactly as described. Shipping was fast, and the packaging ensured everything arrived in perfect condition. I appreciate the attention to detail and thought put into this. Would definitely recommend to anyone looking for something reliable and worth every penny. I’m beyond satisfied and would definitely buy again.

Ordered it weeks ago up ahead!!!!!! got my HVAC ducting done so tried to use it yesterday and it is dried up completely the whole bucket just a sticky rubbery stuff useless now my drywall job is on hold

Used this to seal various parts of my air conditioning system. I applied to seams and screws on the air handler in the attic and also to all connections of the flex duct from the sheet metal plenum. The goal was to reduce as much air loss as possible.I removed the flex duct that was held on with duct tape and a screw. It was all installed around 35 years ago and I found old instructions that said to use duct tape which of course today you are not supposed to use duct tape for anything HVAC anymore. I used an old 2" paint brush. You really want one with stiff bristles because this stuff is thick maybe closer to joint compound consistency. I spread everywhere around each start collar really pushing the sealant into the cracks and leaving a thick layer. I put a liberal glob over any screwheads and spread across any places air might pass through such as seams.It was dry enough within an hour to not be pliable anymore but full cure says 24-48 hrs. For me, I was able to do the second coat for most except the thicker spots. I poured a little water into the jug which thinned it so I could get a better spread over the thicker parts and feather out the product. I was working in a hot attic and I found having a separate container with just water helped a lot since leaving the lid off obviously dries it out. Adding water back in seemed to restore even the drier bits along the sides of the jug. I used a putty knife to scrape it back in and it mixed back in to the rest of it easily. I assume after a full cure it no longer accepts water and creates a permanent moisture proof barrier. Otherwise what's the point.I also spread some on the neck of the start collar and then inside the duct so that when I slid the flex duct back over there would be a seal. This is what you're supposed to do. I then put a screw back in to secure the two together. You're not supposed to do that though, you're supposed to use a zip tie and tensioning tool but I didn't feel like spending the money on those things was necessary since the screws held fine all this time. I used paper backed, pressure sealing foil tape to wrap the flex duct and seal it to the collar. Using pressure you get a great seal so no air can get in or out. Another coating of this mastic over the taped edges and I was set. Simply pull the fiberglass back over the collar and against the plenum then pull the outer vapor layer over the insulation to the plenum and I was done.I also redid a bunch of the flex connections to the boots. The boots had riveted edges which could easily pass air through so I spread over all corners inside or out.I have a 5 ton system and with everything I did there is still half of the container left. I liked the white color because I was able to use it on the ceiling diffusers to seal any cracks without worry about the color. I don't know what else this stuff can be used on but I'm going to find out.

The mastic is easy to apply and quickly seals leaky AC ducts. It works better than tape as it gets into folds and crinkled duct connections where tape can’t form a seal.

Dose the job and seals great

Used the Red Devil F-Seal 181 sealant to seal up around some flex duct terminations on a small HVAC project I was working on. Easy to apply, set properly in the indicated time, happy with this product allowing me to finish things out like a pro.

Don't buy this mastic! It shrinks and cracks like crazy, even when applied thin. Completely useless. Worse than useless! It was a smooth consistency out of the tub and went on like normal mastic. It seemed OK at first but was a complete disaster the next day. Nearly every seam has cracks. It even cracked where fiberglass tape was used, just awful performance. Buy Hardcast, Ductmate, or any other reputable brand that you would find at an actual HVAC supplier. Mama says this stuff is the DEVIL!

I didn't use fiberglass mesh but shouldn't be an issue to do so. Goes on easily. Dries quickly. This stuff is not ruined if frozen. May be overkill but painted inside and out on a short run. Airtight!

I purchased this mastic in order to seal all of the joints in my heating and return ducts that were accessible in my basement ceiling.It was exceptionally easy to apply…much like spreading toothpaste with a paint brush. It goes a long way! The mastic did not have an odor, and it dried very quickly after application. This job took me a few days to complete, and I used a new brush each day. I also put a layer of plastic wrap on top of the mastic before closing the lid with a rubber mallet each day, and this kept the mastic from drying out.Because the majority of the duct work in my basement is up in the ceiling between the joists, and close to the plywood of the flooring above, I adapted some cheap 2-inch paint brushes so that I could actually brush the mastic on top of the joints. I bought cheap paint brushes that have wooden handles, and I trimmed the bristles quite short. Then, I cut off about half the length of the wooden handles with a hacksaw, which made little “stubbie” brushes. These shorter brushes allowed me to apply the mastic at the top of the duct work, and they made the application easier and more affordable.I do recommend that you wash the joints of the duct work before applying the mastic so that the mastic adheres well. I actually washed all of the outer surfaces of my duct work before starting this job, and I was stunned at the 38-years of dirt and dust that I was able to wash off. I also wore disposable vinyl gloves when applying the mastic, as doing this job was quite messy. It was, however, easy for me to rub the dried mastic off of my skin with hot, soapy water.After the whole job was finished, my husband and I definitely noticed an improvement in the heat flow in our home. No more cold spots upstairs in the bedrooms, and no more hot spots in the basement due to leaky ducts. I hope we also notice a change when the air-conditioning is turned on this summer!

I used this duct sealant to seal seams and joints on approximately 250 feet of spiral pipe and assorted fittings and blast gates on my workshop sawdust collection system. I had a multitude of pipe joints, and size transitions from 8 inch duct down to 4 inches, along with a myriad of bewildering elbows and gates.The item performed as advertised, spreading easily across seams and joints and providing an airtight seal once properly cured.I found the application easiest with a cheap chip brush-aka a worn out paint brush with all but the first 1/2 of bristles brush cut off. Between this and latex gloves, I managed to properly seal every joint (inside and out) on the first try. School of hard knocks tip: keep a bucket of water and an old rag handy-this stuff is capable of coating a rookie installer in a wonderful layer of sealing goodness. However, I found that working cleanly and efficiently drastically reduced the amount of after the fact cleanup necessary.The hardest part of this process for me was waiting 24-48 hours for the duct sealant to cure before testing/usage. I used a few incense sticks to test for leaks, using the smoke to test for drafts/leaks within the vacuum system.Bottom Line Up Front: it works well, cleans up easily, and is relatively inexpensive. I have 3/4 of the large pail left-for future expansion projects.

I'm not sure why this is impossible to find at DIY stores in Canada, but I will NEVER use tape again... if I can help it.This goes on like pancake batter and dries to a firm rubber consistency. If you embed fiberglass mesh tape in this mastic (I used fibaFuse mesh tape, found in the drywall section) this makes for incredibly strong and completely air-proof joints.It's messy as heck, but worth it!

Easy to use but can be a bit messy on arms and hands if not careful. Seals duct work seams for better air flow and leakage thru out the house.