How long do you have to wait to sand a 20 minute mud?

1 years ago

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I don't do a lot of drywall, but I do have to do a bunch of patching when insatalling trim, cabinets etc.
The guy who was working with me was mudding up a patching a closet with 20 min mud and it didn't dry for sanding for about 6 hours. Does letting it sit in the pan for a couple of minutes after mixing decrease the "curing" time?
Do you guys have a preferrred brand of hot mud?

Thanks
Tim
Nothing simple is ever easy
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Re: Hot mud--quick question
I never used 20min We always use 90min. It gives us plenty of working time.
I find that even though it sets up in 90min, it still has a high moisture content. You don't want to mix too much water, so maybe that is your problem.
We have gotten away from sanding (almost) and can skim a second coat over hot mud the same day. We have really refined our technique which has saved us lots of time. Keep in mind we are remodelers, so most jobs are done in house. I don't know what strictly tapers are doing.
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Re: Hot mud--quick question
colevalleytim--
The brand of hot mud I use is "USG EZ-Sand", available just about anywhere. Another brand you may see is "Hamilton" which also works well, is even easier to sand, and costs a bit less.
A hot mud's "speed" (20 min., 45 min., 90 min., etc.) refers to approximately how long it takes to harden or "set" before you can coat over it again, not how long it takes to dry before you can sand it. If the coat applied is thick enough, it could easily take hours before it's dry enough to sand. I'm guessing that was the case with the closet patch.
I've wondered myself about your other question: "Does letting it sit in the pan for a couple of minutes after mixing decrease the "curing" time?" I know that USG's mixing directions say to mix the mud thicker than desired, let it sit about a minute, then add water and re-mix to achieve the final working thickness. I'll stay tuned so others on this forum can explain the how and why of that.
--Ken
PS: Unrelated Trivia --> Craig Newmark (of craigslist fame) lives in the Cole Valley neighborhood of San Francisco. You've got a famous neighbor!
Last edited by CaliforniaTaper; 11-10-2007, 02:05 PM.
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Re: Hot mud--quick question
Hmm. My post seems to have disappeared.
Closets have no airflow. Hot mud chemically sets or hardens, but dries by standard evaporation. Apply a fan or a heater/fan combo to add dry air to area and then remove it.
Since it sets faster with heat and slower with cold, and the curing process releases heat, keeping it in bucket or pan, will cause it to set faster. Spreading it out will let it cure slower. Re-Tempering is not recommended or even possible with the WestPac brand, formally Hamilton's.
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Re: Hot mud--quick question
I use a lot of setting muds. I use both EasySand and Westpac Brands . I use 5 min and 20 min for patching. It depends on the size of the patch. I also keep 45 (USG) and 40 ( WestPac) and 90 min. So I can use the material that suits my purpose. I obviously mix less of the faster muds.
As to sanding it. It all sands better dry. Dry might take a while. A fan, or for small areas, a hair dryer helps. I have found that I can slick down the last coat almost as smooth as smooth plaster if I trowel it wet just as it sets. I use a spray bottle and mist it and then trowel it just like I would whitecoat plaster finish. Then right after it sets before it has fully cured and dried I can rub the edges with a damp cloth and get the same result as waiting for it to dry and sanding.
For me hot joint compounds work more like plaster. Since plaster is what I am used to that is what I prefer in joint compounds, too
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Re: Hot mud--quick question
I've been using more and more hot mud for my remodels. It's nice to go in and get a small job done in one day. As has been said, it sets up quick, but doesn't dry for sandability very quick at all. Though with a good trowel technique you can work through it and even texture the job before things are completely dry. It doesn't shrink so you don't have to worry about hollow spots forming later.

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Re: Hot mud--quick question
Hot mud is finicky .. It will harden quicker if left sitting in a bucket however it's a varying and sometimes quick "flash" over to non workable mud once it starts setting up..Sort of like todays cordless batteries. One minute, the impact is driving a 3" deck screw with no hesitance, and a few minute later the impact stops driving. It's not a steady timed event for the mud to setup.
I use a few strategies along with heat/fans to speed up a patch job.
1. I use a power mixer. I start slow and as soon as the mud seems to be smooth, I run the mixer for an extra few minutes at a higher speed.
2. I mix a batch, let it set, dump it... I then Mix a new batch in the same unwashed container.. The mud will set quicker. I've had 45 set to unworkeable in under 15 minutes..
3. 5 minute mud sets in 5 minutes.. follow 2 above and it will set hard in 2 minutes....
hot mud set time is sometimes different from bag to bag of the same time range. I purchase from HD, Lowes and small hardware stores. My hunch is that the product sits around too long and/or in areas that do not have good consistancy with humidity control..
Every day Pros' Are the bags from Drywall Supply Stores are any better?
Hot muds' are great for efficiency. It's worth the time and effort to go through the learning curve..
Last edited by StephenS; 11-10-2007, 09:38 PM.
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Re: Hot mud--quick question
When using small batches, you should dry mix the whole bag because the curing elements tend to settle during transit or riding in the truck for an extended period. That's why whole bag mixes aren't a problem. Remember getting this from USG rep.
SteveC
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Re: Hot mud--quick question
Originally posted by colevalleytim View Post
it didn't dry for sanding for about 6 hours.
Tim
When this first happened to me, I blamed it on trying to use an old bag that had been kicked around and opened and maybe left open more than it should have been. Now I keep the bags rolled shut and if they are not empty after a couple of patch jobs, they go in the trash. For the price of a bag It is not worth taking a chance.
I've never used gypsum accelerator to speed up drying. The results look amazing:
http://www.usg.com/USG_Marketing_Con...tion_Guide.pdf
At the Las Vegas Show, Myron did all his demonstration drywall patches with 5 minute fast set
....Bob Lavery
"One should not make more assumptions than the minimum needed."
William of Occam quote
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Re: Hot mud--quick question
Thanks for the info guys. i had no idea about the settling, the 20 min bag was from the local hdwe store--probably a little old.
As for Craig, see hi all the time, nice guy.
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Re: Hot mud--quick question
Originally posted by SteveC View Post
When using small batches, you should dry mix the whole bag because the curing elements tend to settle during transit or riding in the truck for an extended period. That's why whole bag mixes aren't a problem. Remember getting this from USG rep.
Great info.. Thanks.

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Re: Hot mud--quick question
FWIW,
I dump my bags (20, 45, & 90) in 3 1/2 gal pails (tile mastic, perfect size for 25 lb bags) with lids. Remember to mark each pail and lid for easy ID !! I also picked up some 1 cup aluminum sugar scoops (better than a 4" Spackle knife for transfer) for each pail. Easy to use, easy to dry mix and easy to store.
PS--tile mastic was used for tile, not skim coat ;)
SteveC
The improbable takes time, the impossible takes a little longer.
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Re: Hot mud--quick question
I store the mud just as you do Steve and never have any issues.
One question for those that mention hair dryers and fans to speed drying. I though the "hot mud" sets up chemically and not just by moisture drying out. Does air movement really help dry hot mud?
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Re: Hot mud--quick question
I have never seen the accelerator. I have used plaster of paris and 20 minute to get a faster set. Or just use plaster of paris for the first coat, dries in like 3-5 minutes and then a skim of 20 minute. Only problem is the faster the mud it seems the harder it is to sand. So be careful and sand as little as possible.
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Re: Hot mud--quick question
Originally posted by davenorthup View Post
One question for those that mention hair dryers and fans to speed drying. I thought the "hot mud" sets up chemically and not just by moisture drying out.
Does air movement really help dry hot mud?
yes..
The hot mud seems to chemically harden in most any condition. The air movement and heat does help, though the claim to fame is both speed up the dry out process from solid to sandable/finish ready.
Last edited by StephenS; 11-11-2007, 04:28 PM.
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How long does it take 20 min mud to dry?

Factors in your house like air temperature and moisture content cause the mud to dry faster or slower. For twenty-minute joint compound, though, it'll generally occur after about 15 minutes.

How can I make my 20 minute mud dry faster?

How to Dry Drywall Mud Faster.

Apply light coats (thin layers) Lighter coats of joint compound dry faster than thicker applications. ... .

Run a dehumidifier in the room. ... .

Use hot joint compound. ... .

Using a drying gun. ... .

Sand each layer properly before applying a new one..

How long does mud have to dry before sanding?

Joint compound should generally be allowed to dry for 24 hours between coats and before sanding, painting or priming. High humidity levels and warm temperatures both increase drying times, however.

long wait sand minute mud