I started by using my electric router shaping an accurate radius from the 9mm MDF.
For this pattern I was trying to create a maritime/diving theme so for the plaque frame I used some plastic rope glued around the pattern.
After the rope was in place I used a filler to create a "draft" (angle), draft in sand casting means to create an angle so the pattern will not break the sand mould when lifting it out of the flask.
After the pattern base was ready I started designing the layout of the letters and images. For the letters I used children sticky foam letters, the letters works very well I used them before when I made my FlamingFurnace plaque casting. The images I got and printed are from the Internet, I glued them to 3mm cardboard and cut out the shape after glue dried. I live near the sea so from time to time my son collects shells on the beach so I used a few of them for this casting. The "challenging" shell was the spiral shape shell because I had to create the draft around it. I had to grind the base nice and flat to achieve that so I used my light-duty grinder and it was perfect for the job. At this stage it was just a case of re-arranging and marking every item to the exact location on the plaque. Gluing all the parts, creating a draft around each item with filler and finally and most important thing was to give the plaque pattern two coats of clear varnish. The varnish will prevent the sand from sticking to the pattern during the sand moulding process.
The sand moulding part was easy and successful without any sand breaking issues or other moulding problems. For this moulding I used Petrobond sand because I wanted to achieve a fine finishing for this specific plaque casting.
I used a large wooden flask with inner support ribs for this casting. As always I add a sprue and riser extension as it works very well and prevents aluminum casting shrinkage issues.
After opening the flask and removing the moulding sand I was really blown away at how great and detailed the plaque turned out.
The next part was to cut off the sprue and riser and clean a bit of "flash" (excess aluminum) around the pattern with a metal file. This is an important tip: aluminum alloy is soft metal and can be scratched and damaged very easily so when working with a vice its always a good idea to place the aluminum casting in a cloth and not directly in the vice, a cloth will prevent ruining your hard work. The only casting part that I polished was the letters, diver images and I semi polished the shells. The image with the spirit level below is just to show how flat the back of the casting plaque is with zero shrinkage thanks to the large sprue and riser.
The last and final part was to drill two wall mounting holes and paint the aluminum plaque dark blue.
