Practicing Plastering - Backing Coat
Application of the backing coat can be easily practised and the materials re-used time and time again.
Instead of using sand & cement - substituting the cement for lime will ensure the mix will never set. It will harden if allowed to dry totally, so therefore if it is scraped off the wall the same day and stored in a way that will prevent it drying, (buckets with lids or polythene to cover) then it will last for many applications. (When you come to re-use just add as much water as needed to obtain the right consistency once more).When you actually want to plaster for real then simply adding some cement to the mix will ensure it can be used for a permanent job.
You will notice no obvious differences to sand / lime and sand / cement. All the procedures will be able to be practised in exactly the same manners as in the manual, other than floating. The floating stage can take place when the plaster has firmed up a little. Therefore as the sand / lime mix does not set it will only firm up as it dries this could take some time on a low suction wall.
Practicing Plastering - Skimming
The skim plaster will not be able to be re-used, but a bag only costs around £5.00 and will cover 10 square metres. £í0.00 or so could provide you with at least 3 practice sessions.
A Few Points To Keep In Mind!
If you're feeling confident
Then have a go for real, the following pointers should help you:
Before you start
Don't tackle anything too big – pick the smallest wall first
Have a clear idea of the 6 stages and what you are going to be doing
Mix to the right consistency – keep it thin
Thin coats of only 2mm
Keep it flat – don't leave any bulges
The angle of your trowel combined with firm pressure is vital. Think of 10 - 15mm mm on the leading edge (front edge) as being neutral. Any more than that and plaster will be scraped off, (which is good if you do have any thicker areas or bulges) and will collect on your trowel until which point you flatten your trowel in again when the plaster will be deposited back to the wall.
If you're ever going round and round in circles then it is probably too wet and needs to firm up a bit – give it time.
If it goes wrong
If you followed the above advice then the plaster will only be 2-3 mm thick which will hopefully not be a problem to add to, by applying another coat of PVA and having another go.
If you're not feeling so confident
As the plaster will set it is not advisable to practice applying it to a permanent wall. A temporary wall can easily be prepared by temporarily fixing a sheet of plasterboard to a wall (in a way that ensures it can easily be removed when practising has been completed). If you do nothing else on your practice session other than keep the plaster flat then at least you will be able re-use this practice wall. Once one session has been completed simply paint a weak solution of PVA over the wall to ensure it can be used again. If the PVA is too strong you may lose any suction that the wall had, so it may therefore be better to apply a very weak solution 10 parts water to 1 part PVA, then do the suction test and another coat of PVA can always be applied if it proves to be too dry.
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The author cannot accept liability for the use of any of the materials or methods recommended in this manual or for any consequences arising out of their use. The author cannot guarantee the suitability of any recommendations made in this manual and shall not be under any legal liability of any kind in respect of or arising out of the content of this guide.