Hi there and welcome back to my blog!
This week's blog is going to be about the process of the gel coat and creating the fibreglass jacket.
As you can see from Figure 1, the correct PPE MUST be worn when working with dangerous chemicals like resins. The room must also be well ventilated - this room had many extraction fans which made it a safe environment to work in according to Health and Safety.
Figure 1: Applying Polywax (O'Connor, 2021).
Gel Coat
Figure 1 shows the beginning stage: applying Polywax to the board to ensure that the fibreglass jacket and gel coat can lift easily off the board, because if this was not applied then the fibreglass would fuse itself to the board and
Figure 2: Mixing the Resin and Pigment (O'Connor, 2021). would be extremely difficult to get off.
For a half head cast, 200g of gel coat resin is mixed thoroughly with the catalyst. The catalyst can be measured anywhere from 0.5% - 5%. The higher the amount of catalyst, the faster the resin will set because the catalyst causes the reaction and if there is more of this then it will get to work quicker. 0.5% catalyst was used in this case as it was the first time doing this so was likely to apply it slower than the average application. Pigment can also be added to give the gel coat a colour, Figure 2 shows a grey pigment being added to the mixture.
Figure 3: Applying the Gel Coat (O'Connor, 2021).
Figure 3 shows the gel coat being applied. Here it can be seen being applied with a brush, which stops the liquid from dripping and potentially running off the board. The brush gives more control than if you were to just pour the mixture on. Lots of care was taken when applying the brush coat layer to make sure all of the edges and corners were covered with the mixture. Any gaps or breaks in the gel coat could cause it to crack and break. Similarly, if not enough gel coat is applied this can also cause cracks. Figure 4 shows the final gel coat layer finished and left to set. As you can see, the gel coat has been done very neatly and has been applied all over the core. There are no gaps or breaks in the gel coat, which will make a successful gel coat.
Fibreglass
The next stage was to create the fibreglass jacket.
Prior to doing the fibreglass layers, the fibreglass should be torn and prepared. These pieces should not be cut by scissors and in straight lines as this will make clear edges and can cause air bubbles.
Fibreglass is an extremely strong material whilst also being lightweight, which is perfect to create a jacket for a head cast. Plaster jackets Figure 5: Applying Fibreglass Layers (O'Connor, 2021). can be made, and would be more cost efficient, however, this would mean that the master mould would be incredibly heavy. It was good practise to use fibreglass and has added a new skill to the prosthetic/special effect skillset already shown.
For a half head cast, 1.2kg of resin should be used with 0.5% - 5% catalyst. Again, in this instance, 0.5% catalyst (6g) was used so it could have the slowest reaction time possible, allowing for more time to work with the product as it was the first time ever working with this. Working with 800g resin to 4g catalyst as a first batch and then 400g resin to 2g catalyst for the second batch, meant that there was more time to work because it allowed for the fibreglass to be done in two. If the whole batch was made all at once, then the resin would have started setting before the fibreglass layers were complete.
3 layers of fibreglass was applied around the whole mould, 3 sections were worked on (top of the head, around the head and on the base) in order to keep track of which part was just done. Figure 5 shows a time-lapse of the fibreglass layer process. Both sides of the fibreglass were laminated with resin before being stippled onto the cast. The stippling motion helps to get the air bubbles out. On the final layer, smaller sections of fibreglass are used particularly when moulding around the keys because they need to be very strong. This is the most difficult layer of fibreglassing because the keys need to be moulded around, but also get rid of air bubbles and it is quite difficult to do both.
Figure 6 shows the completed fibreglass jacket. The fibreglass has been layered up well and is a similar thickness the whole way round, there are not any parts that look like they do not have enough product built up on them. The keys have been moulded around well and there are no visible air bubbles. For a first time at working with fibreglass, the result is successful. The fibreglass layers did however take quite some time to do. If this was ever to be created again, time management should be worked on and improved because it took far too long to do 3 layers of this. The fact that there was a pause halfway through to make more resin probably did not help with the timing, but this needed to be done as the mixture would have started setting before the layers were complete.
Thank you for reading this week's blog! Next week we will be cutting this fibreglass jacket and creating a new core ready to begin sculpting!
See you next time,
Alysha :)
Reference List:
O'Connor, A. (2021) Applying Fibreglass Layers [Video]. York
O'Connor, A. (2021) Applying Polywax [Video]. York.
O'Connor, A. (2021) Applying the Gel Coat [Video]. York.
O'Connor, A. (2021) Fibreglass Jacket Complete [Image]. York.
O'Connor, A. (2021) Gel Coat [Image]. York.
O'Connor, A. (2021) Mixing the Resin and Pigment [Video]. York.
Comments