Plaster 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

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.