I'm doing some plastering and finding that my paper tape is bubbling under the wet plaster. The bubbles are quite obvious and unsightly, and of course when I sand it the sandpaper it cuts right through the tape and leaves hairy streaks on my joins. This has never happened before.
Anyone know what I'm doing wrong?
It sounds like the joint compound is partially drying before the tape goes on.
It might be that you are too slow putting the tape on after you have spread the joint compound along the seam. If the compound starts to dry a bit then the paper tape doesn't stick properly and will bubble up later on.
You can stop this by doing the seam in shorter sections so it doesn't dry as much. (which is what I did)
The experts tape a long seam in about 60 seconds flat so drying is not a problem. It looks real easy but it's like everything else in life, it's only easy if you do it every day.
Apparently you can also wet the tape first but I didn't try this so I don't know how effective that is.
For big jobs it's probably best to put up the gyprock yourself but then get in a real person to tape the joints. They do it fast so it doesn't cost much and the job looks far better. 
Anotehr option is to use the joint tape that is a mesh. Its heaps easier for less experinced punters. I have done quite a bit of flushing even though I'm a carpenter
Dont use mesh, its rubbish, more likely to crack
Put slightly more compound under the tape, you can always push the excess compound out along the joint when you bed the tape with the trowel, wont bubble this way
Bed the joint with compound, flatten it off, pre cut the paper tape to length, get the tape started in the joint about 300mm long, while holding the tape in one hand feeding, trowel along the joint, keeping the tape feeding straight, this way you push all the excess compound out as you go and the tape is bedded properly, go over the joint again with more compound if needed straight away, then 2 more coats fo plaster as manufacturers rec.
If you do get bubbles later let them dry, cut them out and fill
Or get someone else to do it and you can blame them
Thanks for the help guys. I think pweedas has hit the nail n the head. I'll have to redo a bit to test and see.
Only use paper tape in internal corners . Or you can also use metal internal corners
Use a sloppy mix to bed the paper tape in the corner using the corner tool
Always use mesh tape on all rebated and butt joints .
2 base coats , 1 top coat then sand
I use mesh tape on all joints. External joints use the bead.
Paper tape, will bubble if mixture is drying as it is applying.
had a similar problem working near a warm ceiling, the ex gryprocker at the shop said to make sure you squeeze all the air out as you run the spatula over it all . lay it on with a metal spatula the same width of the tape, then next layer of base coat has a wider spatula.
here in kal with blasting and the fairly regular earthquakes all the joints except ousde corners are paper tape, the mesh is a bit useless.
dont bother with the all in one compounds, use the proper base coat/top coat system.
too late to strip the bathroom out this season, have to wait till spring, besides i used up all the base coat making a plug for a new landyacht
As Kiterider said , use mesh tape, apply a thin coat , then feed and press the mesh on using a wide paint scraper , using this method will alleviate the bubbling (mesh is much easier ) and make the joining process of joining correctly ( very important because not right means cracking later)much easier , then give a wipe , Gently but firmly ,( if that makes sense ) with a flat square trowell.
Make sure the edges are SMOOTH ! (easier to finish).
There is a trowell with a concave in the working edge which applies more product to the centre of the trowell when you apply the finish coat, this means you have a bit of coverage to sand , and not sand back to the mesh -- not a good look.
Hope this helps
If more info required pm me
Regards cassa
Have been a pro builder for over 20yrs and back to lots of repeat clients etc etc
Dont use mesh tape ever, it was originaly made for patching cracks and holes until lazy buggers got hold of it and used it everywhere, the only reason it gets used is cos its easier to put on(sticky back), it cracks after a while on walls,ceilings,corners everywhere
