What materials are the foams
made from?

Our Azote® brand foams are all made from polyolefins, which is a family of synthetic plastic materials that includes low density polyethylene (LDPE) and co-polymers of ethylene such as Ethylene-Vinyl Acetate (EVA). Specifically the raw materials by grade are:

Plastazote® LD = Low Density Polyethylene

Evazote® EV = Ethylene-Vinyl Acetate (High VA content)

Evazote® VA = Ethylene-Vinyl Acetate (Low VA content)

These raw materials then dictate how the foam will feel and perform, for instance our HD grade foams (HDPE) are rigid, absorb high levels of energy and have good temperature stability, whereas an EV grade foam (EVA) is soft, resilient, but lacks the high temperature stability.

What does ‘nitrogen expanded foam’ mean and how does it
benefit me?

Zotefoams archival grade Plastazote and Evazote are manufactured using a truly unique process technology. This involves dissolving nitrogen gas into a plastic sheet at extreme pressures and temperatures. On releasing this pressure and temperature, the gas increases its volume to such an extent that it expands the plastic into a foam.

Most other foams are made using either volatile / flammable gases or chemicals / blowing agents, which at a certain temperature decompose to produce nitrogen gas (along with other gases such as ammonia). Both of these have negative aspects.

The practical benefits are that Plastazote and Evazote tend to yield far lower levels of volatile substances. This high purity is of great benefit in the packaging of valuable or rare artwork in order to ensure safe transport and storage.

Are the foams able to absorb moisture like a sponge?

The answer is no because archival grade Plastazote and Evazote foams are all ‘closed-cell’, whereas ‘sponge’ materials may be classified as ‘open-cell’:

In closed-cell foams the plastic is the only continuous phase (this is like having millions of small bubbles of plastic all bonded together) and therefore the gas in the foam is trapped inside the bubbles.

In open cell foams both the gas and the plastic are continuous phases. In this case when you squeeze the foam you expel all of the gas from the structure, but when you release it (like a sponge) it sucks air back into the structure.

Practically this means closed-cell foams will not absorb significant amounts of water or other liquids.

Is archival Plastazote truly safe for conservation purposes?

Foams expanded using chemicals often contain residual traces of the blowing agent, which can leach out, causing corrosion, staining and discolouration.

Because Plastazote is manufactured using pure Nitrogen as the blowing agent, it has no propensity to stain or corrode.

To quote Collections Link, the national collections management advisory service: “Plastazote is a dense, inert polyethylene foam that is available in a range of densities and thicknesses. It contains no harmful additives and the foaming agent is ozone-friendly”.