For example, it should be obvious that allowing fingers to dangle near Hollander beater blades can have severe consequences. The following observations cover less drastic concerns, but they are important nonetheless. Since the papermaking process involves large amounts of water, be cautious of slippery surfaces and electrical hazards. Wear rubber-soled shoes and take care to avoid splashing water near extension cords or electrical outlets. Additional concerns arise once you start adding things to the water.
Some plants cause skin irritation.
Add alkali to the water, not the other way around. Some pigments can also be hazardous. Wearing gloves or skin-barrier cream and goggles is prudent when using any chemical additive. Having protected your skin and eyes, don't neglect your ears and nose. Earplugs will bring the sound of a noisy beater down to tolerable levels.