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20 min mud in full bucket of water to prevent drying?

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09-20-14, 01:41 AM   #1  
20 min mud in full bucket of water to prevent drying?

suppose you mix 2 gallons of 20 minute drywall mud in a 5 gallon bucket and there's like 3 cups of mud left in the bucket while you're busy doing something else. Can you fill the bucket with water before it cures and then add more plaster powder to the water and re-use the previous mud that you watered down, or is it a sort of one-time use thing and you have to throw away what you don't use within 20 mins? thanks.

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09-20-14, 04:06 AM   #2  
I couldn't spread half a gallon of 20 minute mud in the allocated time before it begins to harden. Two gallons is way too much. I usually only mis a tray full at a time. Short answer, no, you can't reconstitute it. It dries chemically, and you would only have a clump of broken pieces in your new mix. Why 20 minute mud? It is usually only used in small quantities for repair work.

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09-20-14, 04:38 AM   #3  
I like the 20 minute mud for patch work but like Larry, I just mix up what I need in my mud pan. You have to use up what you mix before it sets or throw the remainder away! If you were to mix it in with new mud [any type] you'd contaminate [ruin] the new batch of mud.

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09-20-14, 06:25 AM   #4  
The other issue of adding more mix to an existing batch is the new mix will harden at the rate of the first batch. So, if you mix up some 20 min mud and after 15 mins you add some more to the mix, the new mud will only have 5 mins to work with it.

It is always better to toss the old mix and start with a clean bucket.

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09-20-14, 07:16 AM   #5  
20 minutes refers more to the "time till you can sand" and full cure rather than 20 minutes "open time". It will usually set up in the pan while you are working after around 5 minutes. You can speed the 20 minutes with a hair dryer if you are in a crunch for time (such as a quick repair).

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10-10-14, 01:11 AM   #6  
I see mostly its been covered, but I have two cents loose on the coffee table, so...

No is the correct answer.

Often on the internet there are language barriers, and when it comes to plaster its terrible.

Important things to remember.

Plaster is a medium, but not limited to a specific set of ingredients.

Read the Bag or Bucket, see what the main ingredients are.

If its Gypsum, it may well give the chemical name of Calcium Sulphate Hemihydrate

If it says this then what you have is in the family of plaster of paris. Once you add water its a one time thing. It wont dry, it will set.. theres a difference.

If you mix up in a dirty bucket, or use dirty water (like the water you just cleaned the bucket with), or have dirty tools - it will affect the set time in an advanced fashion.

2 Gallons of 20 Set is definitely achievable to apply if you have something like a whole bunch of external corner beads to fill, or perhaps are running a screed over a rough masonry wall.

5 Minute mud is way more fun : )

You can retard the set time with a tiny tiny pinch of citric acid or cream of tartar... it pays to experiment if you've never done it because you can ruin the strength of the plaster. I dont make a habit of it, but my old forman used to do it a bit. There are many tricks similar.

3 Cups of left over 20 Set probably cost you about the same as a mouthful of coffee... just saying.

If you live in a climate like Arizona, you could get away with doing most minor patch ups with an all purpose premixed product in a pail (Sheetrock Total, Black Lid On Pail), this can be covered with water and re tempered once you pour that water off again - because its generally a bad idea to dilute any product... unless of course it does need a little water... again experiment if you are a noob.

Im not from the States or Europe, but am familiar with many of the products available internationally. Usg is huge worldwide though generally only selected products per territory are readily available. We also have the Hamiltons Drywall Products.. mud is mud, the Egyptians have a well documented history of using gypsum and lime, then the Romans had a good play around with concrete.. Theres some basic science, but its pretty basic

Hope that clarifies for future reference.


Last edited by Nigel Stewart; 10-10-14 at 01:16 AM. Reason: spelling/typos
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