# Refractory investment for casting

> Investment is a refractory plaster with silica that surrounds the wax model and withstands the heat of molten metal; it is mixed with water, vacuumed and burned out.

- Source: https://www.711grados.com/en/refractory-investment-for-casting/
- Language: en
- Note: This entry was drafted with the help of AI and is pending review by the author.
- Published: 2026-06-22
- Updated: 2026-06-23
- Translation (es): https://www.711grados.com/es/revestimiento-refractario-para-fundir/
- Author: Sandra Sánchez
- Site: 711 Grados (https://www.711grados.com/)

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Investment is a refractory plaster powder with silica. Mixed with water it forms a paste poured over the wax tree inside a flask. Once set and burned out it leaves a hollow mold in the shape of the piece.

## Properties

- **Composition:** plaster with silica (quartz, cristobalite)
- **Mix:** powder and water in the maker's proportions.
- **De-gassing:** in a vacuum chamber to remove bubbles.
- **Burnout:** in a programmed kiln at about 700 °C.
- **Types:** for gold, silver and platinum, with different temperatures.

## Uses in jewelry

- Lost-wax molds.
- Centrifugal and vacuum casting.
- Casting pieces with fine detail.

## Pros and cons

### Advantages

- Reproduces very fine detail.
- Withstands thermal shock.
- It is the basis of lost wax.

### Limitations

- Used only once.
- Silica dust is hazardous.
- A badly made mix gives rough surfaces.

## Care and cleaning

- Measure powder and water precisely.
- Wear a mask with a silica filter.
- Keep the powder dry and tightly closed.

## See also

- [Casting molds: investment, rubber, silicone and sand](https://www.711grados.com/en/casting-molds/)
- [Lost-wax casting](https://www.711grados.com/en/lost-wax-casting/)
- [Centrifugal casting](https://www.711grados.com/en/centrifugal-casting/)