What Is a Glass Reactor? Structure and Process Uses

A glass reactor is a borosilicate glass vessel, usually jacketed, that heats, cools, stirs and holds a chemical reaction under vacuum while you watch every stage through the wall. We build them from GG3.3 glass in sizes from 1L bench units to 200L pilot systems, for synthesis, crystallization, extraction and distillation work.

How does a glass reactor work?

The vessel itself does no heating. The glass body holds the batch while a surrounding jacket carries heat-transfer fluid from an external unit — a chiller or a heating circulator — and that fluid does the thermal work through the wall. A stirrer keeps the batch uniform: on our 1L to 3L laboratory units it runs at 60 to 1000 r/min on a 40W or 90W motor, with speed shown on a single digital display. A condenser on the lid returns solvent vapor as liquid, and a vacuum port lets you pull the vessel down toward -0.095 MPa, which drops boiling points so heat-sensitive solvents distill gently. Feeding happens through a constant-pressure funnel — 100ml on the 1L, 250ml on the 3L — so you can dose reagents without breaking the vacuum.

Why put up with glass at all? Because it is a window. Color shifts, phase splits, crystal onset, foaming — you see all of it in real time instead of guessing behind a steel wall. For development work, where you are still learning how a reaction behaves, that visibility is worth more than any line on a datasheet. The trade-off: thermal performance lives in the circulator, not the vessel. We confirm the matched temperature-control equipment on every quotation, because a reactor paired with an undersized chiller never reaches its target profile, no matter what the brochure promises.

What is the vessel made of, and what can it take?

Every body we ship is GG3.3 high borosilicate glass — written G3.3 on some of our spec sheets, same material. Borosilicate survives the thermal shock of jacket fluid switching from cold to hot, and it resists most acids and organic solvents, which is why it is the default material for reaction glassware at any scale.

Three numbers define the working envelope of our jacketed glass reactor line in GG3.3 glass. Capacity: standard builds run 5L to 200L, with 1L to 3L bench units below that. Temperature: -120°C to 300°C with suitable external equipment — note the qualifier, because the glass survives that envelope but your batch only goes where your circulator takes it. Pressure: vacuum or normal pressure, with no positive pressure unless we specifically engineer for it. Remember that last one; it rules glass out for certain processes, and we come back to it below.

Single, double or triple layer — what is the real difference?

This is where vendor copy goes wrong most often, so let’s be exact.

Einschichtig is a plain glass vessel with no jacket. Temperature control comes from outside — a heating mantle or a bath. Simple to build, but you cannot circulate fluid, so controlled cooling mid-reaction is off the table. Skip the single layer if your process ever needs to pull heat out, not just put it in.

Double layer adds a sealed jacket around the reaction chamber, and a chiller or heating circulator pumps fluid through it. This is what people mean by a double layer glass reactor, and it is the standard choice for synthesis and distillation because heating and cooling share one loop.

Dreischichtig adds a third wall outside the jacket. Here is the point most listings get wrong: the third layer is not a second heating circuit. It is an insulation layer — an evacuated space that cuts heat loss to the room and keeps the outer wall near ambient, so operators do not burn or freeze their hands. It adds no heating power. It keeps the jacket’s work from leaking away. If a supplier pitches a triple layer glass reactor as “faster heating”, ask what the third layer actually connects to. On ours it connects to nothing — it is a sealed vacuum insulation space.

Buy the triple layer for heat retention and operator safety, never for extra heating power.

How do double and triple layer models compare on real specs?

Brochures talk layers; spec sheets talk numbers. Here are our two laboratory series side by side — the double-layer SF-1L to SF-3L models und the triple-layer SFS-1L to SFS-3L models — straight from the parameter sheets.

Read the table and one thing stands out: motor power, stirring speed, funnel sizes and vacuum rating are identical across the two series. The third layer changes thermal behavior, not agitation or dosing. Choosing between them is therefore a thermal question — how much heat can you afford to lose, and how safe must the outer wall be — not a stirring question. We position the double-layer units wherever a jacketed vessel needs circulation support from a chiller or heating circulator, which covers most standard synthesis and distillation work.

On the details: the SFS-1L to SFS-3L lid is 150mm with a 40# flange stirring port, and its sheets list a φ42mm condenser across all three sizes. Scale up and the larger double-layer SF-100L to SF-200L models carry a 340mm lid with a 60# flange stirring port.

Which processes belong in a glass reactor?

Our application list reads reaction, crystallization, extraction, distillation and process development — and each one uses the glass differently.

Reaction and synthesis is the everyday case. The sizing question is not the vessel but the heat: how much your reaction releases decides the jacket and circulator capacity. That is why we ask for your target material temperature before we quote — the vessel is the easy part.

Crystallization is where glass earns its keep. You watch nucleation start instead of opening the vessel to check, and controlled jacket cooling holds the supersaturation curve you actually want instead of the one the room gives you.

Extraction benefits from the same visibility: the phase boundary is right there, so you stop the drain at the interface instead of guessing at it.

Distillation and solvent handling turn the reactor into a still. Vacuum down to -0.095 MPa plus the lid condenser handles solvent recovery, and the limit you will hit first is condenser capacity — so we size the condenser together with the vessel, not after it.

Process development ties it together: run a 1L to 3L unit, learn how the chemistry behaves in full view, then scale into the 5L to 200L line. You can browse the full glass reactor category to see how the sizes step up.

When is a glass reactor the wrong choice?

Be honest about the limits. Positive pressure first: our standard glass line is rated vacuum or normal pressure only. If your process must hold pressure above atmospheric, stop reading glass catalogs — that is a stainless steel conversation, and we lay out the trade-offs in our stainless steel reactor vs glass reactor comparison. Scale second: our glass line tops out at 200L, so beyond that you are in steel territory anyway. And severe abrasive duty — hard solids grinding the wall through long campaigns — wears glass in a way it never wears steel. For everything else at laboratory and pilot scale, visibility and corrosion resistance usually win the argument.

How do you size and specify a glass reactor?

Five decisions, in the order we walk through them on an enquiry:

1. Working volume. Bench work sits in the 1L to 3L SF or SFS series; pilot work runs 5L to 200L. Do not buy a 3L vessel for a 3L batch — you need headroom for the stirring vortex and reflux.
2. Layer structure. Decide on heat loss and operator safety, not on “more layers, more heating” — the third layer is insulation, as the comparison above shows.
3. Vacuum. If you strip solvents or distill under reduced pressure, confirm the -0.095 MPa rating and the condenser configuration with it.
4. Temperature profile. Give us the target material temperature, not just the datasheet range. The -120°C to 300°C envelope belongs to the glass; the circulator decides what your batch actually sees.
5. Ports and configuration. Stirring, funnel size, condenser, custom ports and lifting for the heavier assemblies are all configurable, and they belong in the enquiry from day one.

Send us the reactor volume, jacket type, required ports and target material temperature, and we confirm model and configuration before quotation. Our jacketed glass reactor selection guide walks the same checklist in more detail, and our FAQ page answers the recurring configuration questions.

Fragen und Antworten

Can a glass reactor run under positive pressure?

No — not in standard builds. Our glass reactors are rated for vacuum or normal pressure, with no positive pressure unless we specifically engineer the vessel for it. If your process needs pressure above atmospheric, raise it at enquiry stage or look at stainless steel.

What temperature range can a glass reactor handle?

The GG3.3 borosilicate glass handles -120°C to 300°C with suitable external equipment. The vessel survives that envelope; the temperature your batch actually reaches depends on the chiller or heating circulator matched to the reactor.

How much vacuum can a glass reactor hold?

Our SF and SFS laboratory units are rated to -0.095 MPa. That is enough to pull boiling points down for gentle solvent stripping and vacuum distillation.

Is the third layer of a triple-layer reactor a second heating jacket?

No. It is an insulation layer — an evacuated space that reduces heat loss and keeps the outer wall near ambient. It adds no heating power; the single working jacket still does all the heating and cooling.

What power supply do laboratory glass reactors use?

Our 1L to 3L SF and SFS units run on 220V/50Hz with a single digital display for stirring speed. Motor power is 40W on the 1L and 90W on the 2L and 3L.

If you take one thing from this article: choose the layer count for thermal reasons, size the vessel with headroom above your largest batch, and treat the circulator as half the system. Tell us your reactor volume, jacket type, required ports and target material temperature, and we will come back with a confirmed model and configuration — that is exactly what we need before quotation.