Buying Guide

How to Choose a Laboratory Crucible

Five decisions — temperature, material, capacity, shape and lid — determine whether a crucible does its job. Work through them in order and you will land on the right crucible every time.

A crucible is a simple vessel, but the wrong choice causes real problems: a cracked crucible from thermal shock, a contaminated melt from chemical attack, or a sample that overflows and damages your furnace. This guide walks through the selection logic our engineers use.

1. Start with Your Maximum Temperature

Temperature is the first filter because it rules out materials outright. Match your peak process temperature (with a safety margin) to a crucible material:

Peak temperature	Recommended material
Up to 1600°C	Alumina (Al₂O₃) — the economical default
Up to 2200°C	Magnesia (MgO) — for alkaline & reactive melts
Up to 2300°C	Zirconia (ZrO₂) — for precious metals & ultra-high temps

2. Match the Material to Your Sample

Temperature is not the whole story — chemical compatibility often overrides it. Ask what your sample or melt will do to the crucible:

Neutral, oxidizing or acidic → alumina is stable and cheapest.
Strongly alkaline or fluoride-containing → use magnesia; alumina will react.
Molten precious metals (Pt, Au, Pd, Ag) → use zirconia, which resists wetting by metal melts.

Pro tip: when in doubt, tell us your exact melt chemistry — a quick check against known incompatibilities can save a ruined batch and a damaged furnace.

3. Pick the Right Capacity & Size

Choose a crucible whose capacity is roughly twice the volume of your sample — the extra headroom allows for stirring, foaming, thermal expansion and easy loading without risk of overflow. Our catalogues list approximate capacity next to every dimension:

Small / micro (0.4–10 mL) — thermal analysis, small-sample sintering.
Medium (10–100 mL) — routine ashing, calcination and small melts.
Large (100 mL–7 L) — production melting and bulk firing.

All three materials are available in a wide range of sizes — see the full tables on each product page: alumina, magnesia, zirconia.

4. Shape & Lid Options

Cylindrical — the standard, most versatile shape.
Arc-shaped / boat — for horizontal-tube furnaces and coatings work.
Flanged — a rim that supports the crucible in a holder or furnace opening.
Lid / no lid — a lid limits contamination, oxidation and heat loss; use one for metal melting and calcination. Threaded-lid options are available on selected sizes.

5. Atmosphere & Heating Rate

Your furnace atmosphere changes the effective temperature limit and the life of the crucible:

Oxidizing (air) — alumina and magnesia are stable; zirconia’s practical limit is lower in oxidizing service.
Inert / reducing — where zirconia reaches its full 2300°C rating.
Always ramp slowly — rapid heating cracks ceramics, especially magnesia and zirconia.

6. Quick Decision Checklist

Peak temperature below 1600°C? → alumina.
Alkaline / fluoride melt? → magnesia.
Precious metals or 2000°C+? → zirconia.
Sample volume × 2 = crucible capacity.
Lid needed for oxidation-sensitive work.
Ramp slowly; confirm atmosphere with our team.

Still unsure? Send us your temperature, atmosphere and sample chemistry — we will recommend the right crucible or quote a custom size within 24 hours. Contact Scuvette →

Frequently Asked Questions

How do I choose the right crucible size?

Choose a crucible with roughly twice the volume of your sample to allow room for stirring, foaming and expansion. As a rule of thumb, the melt or sample should fill no more than about half the crucible capacity.

Does my crucible need a lid?

A lid reduces heat loss, limits contamination and protects the melt from atmosphere or splashing. Use a lid for metal melting, calcination or any process sensitive to oxidation; open crucibles are fine for simple ashing and sintering where air access is desired.

What crucible material should I start with?

For most general laboratory work below 1600°C, alumina (Al₂O₃) is the economical default. Switch to magnesia for alkaline or reactive melts, and to zirconia for precious-metal melting or temperatures above 2000°C.