What to ask before you buy a case
A vitrine is a small climate. Once you close the door, the object inside is living with whatever is in there with it — the air, the light, and everything the case itself is made of. This page covers the five things worth specifying, in the order they matter.
1. Materials — what the case is made of matters more than what it looks like
Many ordinary construction materials give off acetic acid, formic acid, formaldehyde or sulphur compounds as they cure and age. In a sealed case those gases have nowhere to go. Lead corrodes, silver tarnishes, shell and calcareous material develops Byne's efflorescence, and it can happen within months.
The standard screening method is the Oddy test, developed at the British Museum in the 1970s and still the industry benchmark. A sample of the material is sealed in a vessel with coupons of silver, copper and lead plus a reservoir of water, and held at 60°C at close to 100% relative humidity for 28 days. Each metal answers a different question: silver reveals reduced sulphur compounds, lead reveals organic acids and aldehydes, copper reveals chlorides and oxides. The coupons are then compared against controls and the material is graded for suitability — broadly, fit for permanent use near objects, fit for temporary use only, or unsuitable.
Two honest caveats. The result is a comparative judgement, not a pass mark: assessment is visual and varies between testers, which is why the sector has spent years trying to standardise it. And a test applies to the batch tested, not to every future batch of a nominally identical product. Our Oddy tested collection lists the pieces built from tested material sets, and we can supply the test reports.
If you are testing your own additions to a case — a mount, a fabric, a label — we sell an Oddy test kit.
2. Sealing and air exchange
A case that leaks cannot hold humidity and cannot keep dust out, and the two problems have the same cause. What you are asking about is the air exchange rate: how many times a day the air inside is replaced by the air outside.
- A display case with a plain door and no seal might exchange several times a day. Fine for a ceramic bowl, useless for anything that needs buffering.
- A dust sealed case with a compressed gasket keeps particulate out and slows exchange considerably. This is the right specification for most gallery and retail work.
- A conservation case is built to hold a stable internal climate, which means a continuous seal, a silica gel well accessible without disturbing the object, and a door that compresses evenly along its whole length.
Ask for the figure, and be suspicious of a case sold as "sealed" without one.
3. Humidity
The target is usually somewhere around 45–55% RH, but the number matters far less than the stability. Objects tolerate a steady 60% better than they tolerate a daily swing between 40 and 60, because it is movement — expansion, contraction, and the stress at a joint or a paint layer — that does the damage.
A sealed case is buffered with conditioned silica gel in a well beneath the deck. The tighter the seal, the less gel you need and the longer it lasts between reconditioning. Put a data logger in the case for a fortnight before you trust it, and keep a calibrated hygrometer in there afterwards. We sell both, and our hygrometers come with a calibration certificate, because an uncalibrated one is just a decoration.
4. Light
Light damage is cumulative and irreversible. There is no restoring a faded dye.
| Sensitivity | Typical materials | Working level | Annual budget |
|---|---|---|---|
| Highly sensitive | Textiles, watercolours, works on paper, dyed leather, feather, photographs | 50 lux | Around 150,000 lux-hours |
| Moderately sensitive | Oil and tempera paintings, wood, lacquer, bone, ivory, horn | 200 lux | Around 300,000 lux-hours |
| Insensitive | Stone, ceramic, glass, most metals | No conservation limit — light for legibility | — |
Two more numbers. Ultraviolet should be below 10 microwatts per lumen, and the practical answer is UV-free LED plus UV-filtering glazing rather than filters retrofitted to a hot lamp. And infrared matters too — a lamp inside a sealed case is a heater, which is why case lighting belongs in a ventilated head or outside the case altogether, and why fibre optic is still specified for the tightest jobs.
Our display lighting is UV-free, and the conservation dimmer comes with a lux meter so you can set a level rather than guess it.
5. Security and handling
- Lockable is a collection for a reason — check whether the lock is in the door or the deck, and whether opening it requires two people.
- Glazing. Low-iron glass for colour neutrality, laminated where the public can reach it, acrylic where weight or transport matters. Acrylic scratches; plan the cleaning kit into the budget.
- Access. How does the object go in? A case that has to be fully dismantled to change a display will not get changed.
- Anti-tip. Anything tall and narrow near the public should be strapped or weighted. We supply anti-tip kits with a making-good pack for the wall.
Send us the object, not the dimensions
The most useful email you can write starts with what the thing is. Tell us the material, the size, the weight, how light-sensitive it is, whether it can be touched, and where the case is going, and we will tell you what to specify — including when the honest answer is a cheaper case than you were about to buy. support@homartuk.com
This page is general guidance to help you specify. It is not a conservation assessment of your collection, and it is not a substitute for advice from a qualified conservator.