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Taper edge obviously easier, but inevitable that you will need to joint a square edge.
Easifil 45 or 60, bigger area get the slower stuff, smaller go faster
For square edges use decent scrim (i prety much anyways just gyproc orange, quite chunky think they call it heavy duty?), and then cover the scrim only, thinnest and narrowest amount poss to Bury it. Let it dry. You will get a sag line sticking out down the joint. Sand that off and get it flat but without eating into the scrim.
Now do two a much wider slab of easifil either side. If you were looking at your work in a cross section, the two bits you are adding now form a giant, very very shallow triangle.Have found using a small and then a giant jointing knife /plasterers knife is the easiest. Once tried with my best trowel and was a nightmare. Taper joints you can keep within the taper. Square edges maybe gonna be 100 to 150mm either side of joint?
Folk who are really good at it don't need to sand. For the rest of us, high quality 120 to 240 grit on an random orbit with a vacuum will get it looking decent. Keep moving, long sweeps otherwise it'll look like surface of the moon once its painted and got daylight against it.
BrickMan-
Good point about using a taping knife rather than a float. I learned with a float so that’s what I stick to (Marshall town pre worn stainless finishing trowel for the interested).
But again, the pros seem to predominantly use taping knives.
Learning to widen the joint as you describe was a game changer too. And search on YouTube for how to feather an edge properly. If the edge is feathered badly it’ll be a dusty nightmare getting it smooth. Some people like to get it 90% there, then paint, then fill any small bits with a lightweight filler and touch up with paint again - as lots of imperfections disappear after a bit of paint - but taking the time to get it as close to perfect before paint has always been my preference.
Checking the surface with lights that replicate what will be in the room - angle of natural light and room lighting - is also a good idea. Nothing worse than thinking you’ve nailed it, only for the setting sun to pick up every tiny imperfection you can’t see when it’s lit from a different angle. -
Thanks for the tips.
I have a 6" knife which seems to be working well enough.
Nef
NotThamesWater
Taping & joining plasterboard.
I'm really bad at it, and I don't like doing it.
Which jointing compound should I be using?
I'm assuming that pre-mix is for dilettantes and plastics.
And I've finished one tub in a few hours, so it's going to get expensive unless I start to buy powder & mix it myself.
I'm using square edges & paper tape, if that makes a difference.