Sealing a deep well plate: the seal is half the product
Most storage failures blamed on plates are seal failures: evaporation at the edges, a film that lifted in the freezer, a mat that was never fully seated. Pick the seal for how long the plate sits and how often it opens.
Adhesive films
The cheap, fast default. Foil films block light and evaporation for freezer storage and are pierceable by many automation tips. Their weakness is the bond: adhesive softens with DMSO and some solvents, and a film peeled and restuck no longer seals. Use films for plates that get sealed once and opened once.
Heat seal films
The tightest seal of the three, welded to the plate rim by a heat sealer. Best for long storage, transport, and PCR, where vapor pressure tests the seal every cycle. The cost is equipment and commitment: a heat seal is single use, and removing it is a deliberate act, which is either a feature or an annoyance depending on your workflow.
Silicone cap mats
A mat of 96 individual caps in a silicone sheet, pressed into the wells. Cap mats are the resealable option: pull the mat, pipette, press it back, and the plate seals again, which is why they suit working plates that open daily. Quality mats are pierceable and re-pierceable for automation sampling. Seat them with a roller or applicator so every cap is home; a floating corner cap is a slow leak. Arctic White sells silicone cap mats under its ArctiSeal line for exactly this resealing job.
Seal types compared
| Seal | Evaporation control | Reseals | Pierceable | Best for |
|---|---|---|---|---|
| Adhesive film | Good | No | Some foils | Single use storage, light sensitive samples |
| Heat seal film | Best | No | Some | Long storage, transport, PCR |
| Silicone cap mat | Good | Yes, many times | Yes | Working plates, repeated access, automation sampling |
Related guides
Common questions
Why do the edge wells of my stored plate lose volume first?
Evaporation escapes at the seal perimeter and edges sit closest to it. A fully seated mat or an intact film keeps edge loss small; a lifted corner turns the outer ring into the first casualty.
Can I freeze a plate sealed with a cap mat?
Yes, silicone stays flexible at freezer temperatures. Leave headroom in the well, because frozen samples expand and can push caps up if the well is brim full.