I’ve made the positive with clay, and I’m going to cover it with vaseline and take a negative mold of it with plaster. My question is referring to the next part. I want to make a positive from the already dried plaster negative. I need to know, if the plaster of the positive being made will stick to the negative at any point and if I need to take any precautions, like vaseline or something. Thanks!

To stick: you need to rough up the texture of the plaster that you want to add on to. If it is too smooth, eventually the newer layer will break off of the previous layer. This is something you might do if you were building the layers for your mold and needed to add on after a layer had set.

To prevent sticking: this is for your next part>>>what you want is called a release. You can buy a can of Universal Spray Release, use vaseline in a thin coat, or mold soap. There are many types, just look up plaster and release. Vaseline can be applied with a chip brush, and mold soap can be thinned and applied with water, but you let it soak in and do a couple layers. If you use Murphy’s oil soap or green soap, use 1:1 water and soap, but you have to watch for bubbles. You can use an air compressor hose to blow those off. Some prefer the mold soaps and green soap because of the greasiness in other releases preventing absorption. The other thing to watch for, but this is at the beginning of moldmaking: make sure you placed your parting lines well so you don’t have any draft problems or undercuts aka problems with mechanically locking the mold to the casting.

I threw the Douglas & Sturgess link below. No matter where you are, you can call them and chat them up on their supplies and techniques.

Try in the job centre.

Im just starting out learning how to do plastering and finding it quite interesting.ive been doing it for a few months now and gaining loads of confidence.now the tricky bit?.how do you plaster around the back wall of the toilet m m ?? can anyone provide any tips?
If a low level cistern this can be removed and also the toilet itself. Make sure water is isolated. Then remove the cistern first and then the toilet. This will leave a whole in the wall for the waste outlet. Dont forget that there is water in the bowl of the toilet so becarefull or else it will go all over the floor.If you do a stage at a time top down you will be ok. But you must make sure water is isolated. This then makes it easier to get to the back wall.

How can I find out how to price internal plastering work, ie ceilings walls etc.
Surface area is a guide to quantity – most plaster mixes have a coverage factor (kilos per square metre etc.) Time to apply said plaster including prep, application and finishing, as a labour cost. Then add VAT to the whole total.