# 90 minute mud



## gowings (Nov 10, 2013)

I have a tight deadline coming up on an office reno. I need to move a door opening and finish it asap.
Is 90 actually dry sandable in 90. I assume that means light skim coats.
I was reading the bag
Its says on the bag on the reverse side in small print, sets up in 90 but is sandable next day.
I'm confused.
I always thought a hot mud mix would let me sand in 90 and keep rockin till I'm happy with the finish.
Thanks


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## Golden view (Feb 16, 2012)

Chemically hardens, but dries through evaporation.

Even 5 minute mud takes a day or 2 to dry depending on thickness, humidity, etc.

You can do your next coat as soon as it sets, and you can speed drying with heat.


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## builditguy (Nov 10, 2013)

What he said. 

When we have to get a patch done quickly, we use Durabond for the fist coat. Then Easy sand for the rest. I usually get 45 minute mud. Sanding would have to be done the next day. 

Even with the 45 minute mud, there is some variance in setting times. If we used it all the time, we would probably be better at mixing it to get consistent setting times.


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## goneelkn (Jan 9, 2010)

http://www.contractortalk.com/f49/i-have-some-small-drywall-repairs-do-loong-way-home-274985/


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## Inner10 (Mar 12, 2009)

Crank up the temp, get some fans, dehumidifier...

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## hdavis (Feb 14, 2012)

Use 5 minute or 20 minute for tight deadlines. You don't want to be sanding something like durabond, it sets too hard. Don't leave that coat proud, lumpy, or with a bunch of tool marks, it'll be a pain if you do. You can shave setting compound before it can be sanded, so that can speed things up a little as well.


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## gowings (Nov 10, 2013)

Thanks for your advice.
Merry Xmas


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## MarkJames (Nov 25, 2012)

How tight? Is this a same-day job?

I could see getting the first coat on in the morning, heat gun to dry it fully, then the follow-up coats will be quick and easy. Note that it may look dry from the gun, but moisture may reappear as it gets to the surface. Watch for that and keep at it. Vigorously mix your first coat and it might just dry out in half the time for you, too.

Edit: and keep your sanding to a minimum...that's just more compound to dry anyway!


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## gowings (Nov 10, 2013)

I have 8 hrs in the evening and 3 hours in the am the next day. i can tape it and leave it.overnight till 5pm when i can get back in., Since I have some butt joints from a patch to fill.


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## Sir Mixalot (Jan 6, 2008)

I'd use 20 minute for initial coats. Then skim it with an all purpose for the final coat, put a fan on it and it will be ready to sand, prime and paint. :thumbsup:


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## blacktop (Oct 28, 2012)

Setting muds are not fast drying! 

JS!! Set /Cure/ two different thangs !


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## Tom M (Jan 3, 2007)

Sir Mixalot said:


> I'd use 20 minute for initial coats. Then skim it with an all purpose for the final coat, put a fan on it and it will be ready to sand, prime and paint. :thumbsup:


Why AP? I was doing Light weight but it can be too easily sanded away and soft so I compromised with medium.


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## blacktop (Oct 28, 2012)

Tom M said:


> Why AP? I was doing Light weight but it can be too easily sanded away and soft so I compromised with medium.


Painters hate painting over hot mud!


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## hdavis (Feb 14, 2012)

blacktop said:


> Painters hate painting over hot mud!


Flashing can be really bad on easy sand.


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## Tom M (Jan 3, 2007)

hdavis said:


> Flashing can be really bad on easy sand.


I know. Are you HM & AP too? 

I like the durability of AP but creaminess of lighter stuff to skim.


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## Sir Mixalot (Jan 6, 2008)

Tom M said:


> Why AP? I was doing Light weight but it can be too easily sanded away and soft so I compromised with medium.


Stronger and still sands easily. IMO.


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## Tom M (Jan 3, 2007)

blacktop said:


> Painters hate painting over hot mud!


Most of them use 5 minute and 20 minute. 
I have had a few bad experiences with flashing and peeling latex over HM.


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## Tom M (Jan 3, 2007)

Sir Mixalot said:


> Stronger and still sands easily. IMO.


I must need a newer knife, my six inch is a personal favorite but the camber is mild at best I don't get the feathered edges unless I work wet and loose. Still the heavier muds don't feather as well


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## Sir Mixalot (Jan 6, 2008)

Tom M said:


> I must need a newer knife, my six inch is a personal favorite but the camber is mild at best I don't get the feathered edges unless I work wet and loose.* Still the heavier muds don't feather as well*


Do you thin a little with water to get them nice and creamy?


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## hdavis (Feb 14, 2012)

Tom M said:


> I know. Are you HM & AP too?
> 
> I like the durability of AP but creaminess of lighter stuff to skim.


Durabond or easy sand, then I use either AP or medium weight. Sometimes it's just durabond.


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## hdavis (Feb 14, 2012)

Tom M said:


> I must need a newer knife, my six inch is a personal favorite but the camber is mild at best I don't get the feathered edges unless I work wet and loose. Still the heavier muds don't feather as well


The thicker it is, the harder you have to press and the more curve / stiffer the knife blade needs to be. You have to match all three to get good results easily.

Run a stiff mix, and you'll need to trowel instead of knife it. Thin mixes are much easier to work with.

If you knife won't hold the curve you need, junk it and get one that will.


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## Tom M (Jan 3, 2007)

The couple of smaller knives I tape with are stainless steel and my bigger finishing blades are steel.

Im guilty of not always mixing or thinning. I am usually bouncing between jobs and tasks. not fully focused on just mudding. The jobs I know Im taping and mudding all day I mix and whip nice. I even keep a bucket of water around to dip my knife in occassionally. I get nice edges on those jobs. Its is a big diference.

Today I used both medium and AP. The medium is was wayyyyy to stiff.


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## Tom M (Jan 3, 2007)

My six inch knife is square and probably 20yrs old. Since the beginning I have always grabbed this knife. Its really a favorite. Its way due and has a nick but I sanded the edge smooth. lol I only like round shaped knifes on smaller 4" knives.


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## blacktop (Oct 28, 2012)

It's all in the tools . You can't buy a 5ver off the shelf the first day and make it work.


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## blacktop (Oct 28, 2012)

tom m said:


> my six inch knife is square and probably 20yrs old. Since the beginning i have always grabbed this knife. Its really a favorite. Its way due and has a nick but i sanded the edge smooth. Lol i only like round shaped knifes on smaller 4" knives.


20 years?? In drywall years that's like ....110 !!!


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## Tom M (Jan 3, 2007)

blacktop said:


> 20 years?? In drywall years that's like ....110 !!!


Well I dont rock and tape like you.....I may do it a week or two straight then not again for a couple of months depends.

So I got complacent :laughing:


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## Tom M (Jan 3, 2007)

blacktop said:


> 20 years?? In drywall years that's like ....110 !!!


I have been thinking of marking which side of the knife I should be using because I trouble seeing it by sight at this point:no:


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## Tom M (Jan 3, 2007)

And thanks to your other thread post with the wool roller I dug mine out. I didnt know you could replace the roller covers mines hardened up and after I smacked the hell out of it to loosen it up the cover is worthless.


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## blacktop (Oct 28, 2012)

Tom M said:


> And thanks to your other thread post with the wool roller I dug mine out. I didnt know you could replace the roller covers mines hardened up and after I smacked the hell out of it to loosen it up the cover is worthless.


When the wool wears out ..That's about the time the spool goes too.. I pitch em at that point ... I mean It's only $20 ...If It worked ya 5 homes ? Whats It owe Ya ?


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## hdavis (Feb 14, 2012)

Tom, if you're just going to grab thinned or unthinned and start working, you really need to consider having two sets of knives to handle the different amount of pressure you have to use.

Knives and rollers are cheap. If you aren't replacing your knives with some regularity, chances are you're doing way more sanding or taking way more time detailing than you could otherwise.:no:


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## VinylHanger (Jul 14, 2011)

I used to use the blue steel ones. Grabbed a stainless and it is so much better to me. I usually use a towel for mudding, but I am liking this particular knife a lot.

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## gowings (Nov 10, 2013)

My issues seem to stem a lot of times in patching old to new drywall.
The old drywall was a full 1/2 thick plus the added mud and it seems 5 coats of paint. The new lightweight that is only left now is closer to 3/8 than a 1/2. 
Its a dam nuisance working with it to get it to match the existing finished walls.


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## Philament (Dec 9, 2014)

I've read about people using plaster of paris and ap mud. Does anyone use this method? Does it cure any faster?


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## gowings (Nov 10, 2013)

*YIKES*
I went back to get the finish coat on after cranking up the heat to 85 and running 2 fans on the repair. The paper seam tape cracked on the one edge that was on the painted side of the wall I feathered out on the 3rd coat of reg. mud. The joint itself is fine. The tape was fine after the second coat of reg. mud.
My guess, dried to fast and shrank. would that be a good assumption.
Do I seam that now and re feather it or maybe cut the tape back a bit and feather it out. 1st coat was 90
God It was really rockin along with the advice I was getting.


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## VinylHanger (Jul 14, 2011)

Does ice cold water make 45 minute set up faster? I'm just mudding in a shower stall and it is seeing up like 20 minute.

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## Tom M (Jan 3, 2007)

Hot speeds up the reaction but I believe the bags separate chemical sometimes. I often felt some batches set up faster than others.

I am going to pick up 3 new of my most knife sizes and see how it works out.


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## Tom M (Jan 3, 2007)

hdavis said:


> Tom, if you're just going to grab thinned or unthinned and start working, you really need to consider having two sets of knives to handle the different amount of pressure you have to use.
> 
> Knives and rollers are cheap. If you aren't replacing your knives with some regularity, chances are you're doing way more sanding or taking way more time detailing than you could otherwise.:no:


What would you use steel for thinned and stainless steel for unthinned coats?

Not sure what your getting at.


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## madmax718 (Dec 7, 2012)

I find steel to be more flexible and stainless to be stiffer. I'll do 20 min in small batches, then knife scrape anything sticking out


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## JAH (Jul 27, 2014)

The blue steel is easier to manipulate but keeping it clean is a pia. I have both on hand, stainless is the primary.
Hot mud and green lid are all I use. Im not carrying 3 or 4 different types of mud in for a job.


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