Plaster, Cement and Concrete

Table of Contents

How To

Video / Tutorial

View the video on Vimeo.

Instruction

  1. Preparation:
    • Safety first: follow and wear required PPE (gloves and skin protection, eye protection, optional dust mask).
    • Set up in a well-ventilated area (spray booth when working at the GSD).
    • Ensure surface protection: cover surrounding areas with brown paper.
    • Prepare your mold with mold release and make water-tight, if applicable.
    • Prepare three buckets:
      • a “wet” bucket, for weighing water and mixing dry ingredients into the water,
      • a “dry” bucket, for weighing plaster or cement,
      • a “rinse” bucket, for clean-up of hands and tools.
  2. Mixing:
    • Dry materials should be handled, measured, and mixed in the spray booth.
    • Determine the volume of material needed and the corresponding amount of material.
    • Follow the manufacturer’s instructions for the ratio of water to dry product.
    • Remove or add room-temperature water to the “wet” bucket until desired weight of water is achieved.
    • Carefully scoop plaster or cement into the “dry” bucket until the desired weight of plaster is achieved.
    • Dry material should be gradually mixed into the water with a gloved hand or tool; strew it atop the water and allow it to settle and slake (for 3 minutes) before mixing (for 3 minutes).
    • Once all plaster is hydrated, working in the spray booth is no longer needed.
  3. Pouring: Pour evenly into your mold, aiming at the lowest point to avoid trapping air.
  4. Curing: Allow for overnight cure at room temperature. Note that several days to completely harden and gain strength may be required for fragile geometry.
  5. Finishing:
    • Clean your tools and work area of your mixture immediately, using the “rinse” bucket for tools, hands, and creating and rinsing a cloth rag for wiping surfaces.
    • Allow unused mixed plaster to harden in the mixing container:
      • discard the hardened plaster as solid trash,
      • retain the mixing container for future use, if possible.
    • Never pour anything down the drain, use the non-hazardous waste barrel next to the sink, instead.
    • Fill-out and display a “storage form” if you leave your project to harden where another person may encounter it.

Product List

In general, you should be using products whose Safety Data Sheet (SDS) indicate that the product contains no or only trace amounts of crystalline silica.

Plaster

  • Hydrocal
  • Plaster of Paris
  • Pottery Plaster

Cement

  • Rockite
  • Quickcrete

Required Personal Protective Equipment (PPE)

  • Eye Protection: Always wear safety glasses
  • Skin Protection: Always wear nitrile gloves and long-sleeved clothing
  • Airway Protection: Dust mask to limit particulate exposure

Engineering Controls

  • The handling of dry media (measuring and mixing) must be done in a spray booth or suitable ventilation hood.
  • Store unused material in closed container to prevent spillage onto the surrounding areas.
  • Project must be labeled clearly while hardening.
  • Eyewash stations must be available in the vicinity when using this product.

Emergency Response

  • Eye exposure: Wash thoroughly in the eyewash station for at least 15 minutes.
  • Skin exposure: Wash all affected areas thoroughly with soap and water.
  • Ingestion/ Inhalation: Seek immediate medical attention.

Storage

This material is reactive with water. It must be stored in a safe and dry space so it cannot come into contact with water.

Disposal

  • Plaster and other cementitious materials should never be poured directly down a drain, whether wet or dry.
  • Before working with the material, prepare a rinse bucket for washing your hands and any tool that will contact the material.
  • Leave leftover material to harden in a flexible mixing container and discard it in the trash once fully hardened.
  • Decant excess water from the rinse bucket and dispose of it down the drain. Any leftover material in the rinse bucket should be disposed of as non-hazardous liquid waste (white barrel with yellow top adjacent to sink).

Other Notes

  • Exothermic reactions during hardening can cause plaster to become hot. Do not attempt to cast plaster directly off your body.
  • Be careful not to breathe the dust from sanding. When allowed, use the down-draft table or other methods that limit creation of dust.
  • Always consult the Safety Data Sheet (SDS) for the complete manufacturer’s recommendations and cautions before use.