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I've been reviewing various drywall videos and documentation but I haven't found clear details on what kind of thickness the joint compound should be. Is there a definitive answer for this? Or does it vary? Even videos with "pre-mixed" compounds still mention adding additional water.
Is there a rule of thumb or general guidelines for this?
I found it took me a couple hundred hours of applying mud to get to the point where I knew exactly how I wanted it to look. I learned just fine by starting with the pre-mixed straight out of the bucket and slapping it on the wall. You'll quickly notice the difference in application ("spreadability") when it starts to dry in your mud pan a little bit. Then you add water - too much the first time of course - and the mud will fall off your knife before you can get it to the wall.
Just keep in mind, it might take more than two or three coats, but if you can spread it on the wall you can't really screw up the consistency. If it's too dry, it will crumble as you press it with the knife, if it's too wet it will fall off your knife (and the wall).
Then you add water - too much the first time of course Kind of like learning to mix concrete. There's a fine line between holds a groove when you draw your finger through it and liquid mess. Seems like that last extra pint in the wheelbarrow does the damage.
Feb 2, 2014 at 20:09
Actually...
On the bucket is says mix and apply before adding water. Videos are kak. I'm a trade qualified plasterer blh blah experience etc. What I do is read. Read the bucket, read the data sheets, read books about plaster publishd by plaster companies, read summaries and technical analysis of arbitration processes where products have failed.
So fresh bucket off the shelf : fine Fresh bucket mixed with 500W drill : Perfect
Apparently some companies put less water in the premix over winter to avoid freezing during shipping, which may have an element of truth to it. At any rate the general rule of thumb is that you can add about a cup of water to a 5 galon pail of premix without killing it. Too much water and it becomes what you call friable, what this means is that the paint wont bond to the compound, so you have what l9oks like paint faliure, but its the premix. When you dilute anything you spread all the parts out, then when the water has evaporated all those parts are too far from each other to create a strong matrix.
If its dry bagged it should say on the bag how much water per bag, like I think a 20lb bag of Sheetrock Easysand says something like 5.4-7.1 litres dont quote me on that, but its on the bag so you just use maths and say use quarter of the water for quater of the bag. With drymix the less water end of the spectrum is stronger so good for filling, the more water within guidelines is still strong enough but easier work for second coating.
Your choice of materials depends largely on your climate. Hot dry climate use premix. Cold or humid climate use dry bag.
So yeah I know this is an old thread, but this is something of a PSA too. I like to hunt down weird questions about plaster and give informed answers to prevent the future generations from messing up their job. You could think of me as a whitehat plaster troll if you wanted, or you could just learn to use google better by taking data from packaging and using keywords like data as in technical data sheet. Any industry has its own members associations, publications, forums - it doesn't matter if it's plaster or gasoline, reading will get you further than 99.9% of videos out there... unless you already know the rules and are looking for new ways to break them.
I've always heard it should be the consistency of cake frosting, but I find that to be still a little subjective. It should be smooth and creamy, thin enough to spread easily without falling off your drywall knife.
In practice, I just mix it up until I think it looks close, then start using it, and if it's not going on well I'll adjust the mixture. After applying a couple of pans full you'll definitely be able to tell when it's too thick or thin.
It's going to depend a bit on what you are doing. If you are filling in low spots or holes where you'll be applying a thick coat, use a nice stiff mixture (stiffer than out-of-the-bucket pre-mix).
For a normal first or second coat, I'll usually use pre-mix right out of the bucket without thinning it down at all. Then for the finish coats I'll ad a bit of water to make it spread more easily and get a smoother finish.
If you added too much water you would have more problems than paint problems as the poster above mentioned. But the 1 cup per 5 gallons is incorrect. This is coming from a drywaller with over 30 years experience.
As far as premixed is concerned, it's foolish to think you think you can apply straight out of the box for taping in a bazooka or using a flat coater, let alone getting it through the pump for the coater. All premixed needs water added. The only time you take it straight from the box is for screw heads. Everyone's consistency of water added is different, in cooler climates you may need more water, and in humid climates you may use less along with cement board instead of drywall.
The two key things are spreadability and consistency. If you have done this before, you know what I mean. As far as paint is concerned, that he mentioned I never in over 30 years have never encountered such a problem. If you added that much water to your mud you would have soup running down the wall, never mind painting it as you would have nothing to paint over. I chalk up the paint problem due to not using drywall primer specifically made for new drywall and mud.
