What is best to use on ceilings? Fiberglass or paper?
I am assuming you mean fiber tape or paper tape for taping the seams before applying mud. Fiber tape is the worst thing to use! It may save you some time applying the tape as it is self adhesive but, it will crack almost always.
Paper tape provides a layer equal to the drywall paper and is much stronger.
Fiber tape will fir if it is over sanded and the strands need to be cut as if you pull on them they will run the length of the tape leaving you with a needed repair.
I hope that helps.
I agree with Dale, again assuming that the question is about taping. In the future, be much more specific.
The fibreglass is easier to work with... initially ... because it sticks and the mud squeezes into the mesh. That's about it. The paper hides the seam better and is a best in areas that you might sand agressively. The mesh, if not done properly, can fray and if you were to use it in an inside corner, it tends to not provide as sharp an angle as the paper product.
Take the time and you'll be fine. The key is to make sure the mud is wet enough to provide a good contact between the tape and the surface of the drywall.
Whenever you use the fibre tape, your first coat must be a 50/50 mixture of regular drywall mud & the powder Sheetrock mud, or you can get hairline cracks in the joints. If you are using paper tape then just straight mud is fine. We use Sheetrock 90 when mixing it with regular mud.
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