The slides from my 2 panels are available on google drive. You can find those here:
Gem Magic Slides
Resins, Castings, and Composites Slides
Feel free to contact me via discord (links on the side) if you have questions.
Some notes from the presentations:
Gem Magic
Quartz Safety
Quartz if made of silica (silicon dioxide) and is not chemically reactive and so it is not directly toxic. Silica is everywhere in nature since it is the principal component of sand, but in nature we do not commonly encounter clouds of fine silica dust. Fine dust is not caught by the main defenses of the respiratory system and can reach the deeper areas of the lungs and the alveolar sacs (like other fine particles). Because of silica’s inertness the human body does not have any metabolic process to convert it into a water soluble form (which is how most undesirable substance are removed).
The immune system will attempt to address these particles by forming fibrous tissues around them. This fibrous enclosure interferes with the alveoli’s ability to perform gas exchange. The result is decreased lung function which becomes worse with continued exposure.
In general working with quartz on a faceting machine does produce the hazardous dust associated with silicosis. The diamond laps used in faceting need to be cooled to prevent the diamond from breaking free and to prevent the stone from getting too hot. Other tools, such as angle grinders, can produce this dust and proper PPE should be used when working in such conditions.
There is a related issue regarding engineered stone. These products are normally created by combining quartz powder with resin to create a slab with excellent properties much cheaper than mined stone. Australia has banned any engineered stone product containing greater than 1% silica. However they still permit the working and sale of granite slabs which exceed this limit (granite contains 20-60% quartz).
It is not surprising that Australia, with its large mining business, would prefer to keep cheaper alternatives off of the market. However, examining how these materials are processed reveals where the dangers lie. Mined slabs must be cut with diamond saws which user water cooling for the same reason faceting machines require water cooling. This constant water flow captures the dust from the cutting operation.
Engineered materials can be processed in the same was as mined slabs, with a water cooled diamond saw. In addition to diamond saws engineered stone can also be cut using tungsten carbide tooling. These tools do not require water to keep them cool and can be more cost effective than diamond tools. The lack of water cooling permits the dust from cutting to be dispersed all around the work area. This cloud of fine dust is the cause of the medical issues we want to prevent.
In some cases, especially medical offices, the non-porous nature of engineered stone makes the preferable to their porous mined counterparts in preventing the spread of disease. Engineered stone is just as safe to work as mined stone if it is processed in the same way (using water to address dust issues). Requiring proper dust control would keep workers safe without banning an entire class of useful products.
Resins, Casting, and Composites
Dense Fillers
If using a thin resin in combination with a very dense filler then it is possible for the filler to sink to the bottom of the mold while the resin is curing. Thicker resins may help to address this, or the mold can be continuously rotated until the resin has sufficiently hardened (such as in roto casting).
Textures from Fillters
Fillers such as iron fillings can be used to add texture to a part which were not part of the original mold. Because iron filings cannot evenly fill complex mold shapes there will be gaps where the filler does not reach, resulting in a texture related to the shape of the filler. This can permit the rendering of multiple textures from the same mold, though the process is difficult to predict.
Magnetic Properties of Composites Made of Iron Filings
Any cast which contains significant amounts of ferromagnetic material (such as iron filings) will stick to magnets.