plastering

Always use fresh plaster - even plaster that is still within the use by date, as you have found out, is not always usable, especially not if stored in a shed where moisture from the air can affect it severely

many thanks for advice on previous post on this subject,bought new board finish,applied two coats to the ceiling and a definite improvement resulted,the area skimmed is in a passageway with no daylight and has a radiator ,had to use a halogen light to give sufficient light to work but of course this raised the temperature but i would estimate only to the level of summertime,i had a real struggle to finish as both mixes were going off so fast even though i sealed well before starting,is there anything that i can use to retard the setting time of board finish or am i just too slow applying,many thanks in advance

You *are* plastering the right side of the board?

Artex is much easier to use for the amateur. At least double the price but you get more time to fiddle with the finish