Cork and pin boards: what the material is and how it behaves

A pin board has a surface that takes the pin, with other layers under it. The build of each type is compared in our guide on pin, cork, magnetic or glass boards.

The surface decides how the board feels in use. This guide therefore looks at cork itself: where it comes from, what it is made of and how it behaves when it is pressed. The sources are an Amorim Cork Solutions book and brochure and two academic review papers, all opened on 8 November 2026.

Cork comes from the outer bark of Quercus suber L., the cork oak [1]. Amorim says the stripping is a highly specialised process that does not harm the tree and that the bark renews itself [1]. Its insulation brochure calls cork a renewable raw material [4].

Amorim says bark is removed every nine years once the tree has reached maturity, around 25 years, and that a cork oak can live up to 200 years and be harvested 15 to 18 times [1][4]. The detail of how the harvest works is in our guide on how cork is harvested.

Amorim reports cork oak forests covering 2.2 million hectares in the western Mediterranean basin [1], while its insulation brochure gives 2.1 million hectares [4]. The two Amorim documents differ slightly, so treat the area as roughly two million hectares. Amorim states that Portugal accounts for approximately 50% of world cork production [1].

At small scale, cork is a mass of closed cells filled with an air-like gas mixture, arranged along the radial direction of the tree [3]. Pereira's review gives the cell walls as 1 to 1.5 micrometres thick and the solid material as approximately 10% of the volume [2].

Amorim describes the hollowness from another angle: 60% of each plank of cork is gas [1]. The two figures come from different documents and are worded differently, so do not merge them.

Amorim says the air inside each cell is sealed in by suberin, which is why it describes cork as impermeable [1]. Suberin is the largest single component in all three sources, but its share is reported as 45% to 53% [1][2][3]. Amorim gives lignin as 27% of cork composition [1], while Pereira gives 26% of the cell wall [2]. The figures differ. The sources do not say why, and one possible reason is that they describe different samples or different parts of the bark, so quote the source whenever you use one.

Cork products are not always a single slab of bark. Amorim describes several product families, most of them made from granules that it says are separated by size and density [1]. Sergi and colleagues describe agglomerated cork as cork granules mixed with a thermosetting or thermoplastic resin [3]. The comparison between bonded cork and bark sheet is in our guide on agglomerated cork and cork bark sheet.

Amorim lists agglomerated cork blocks and rolls with more than 90% cork content, and cork rubber at a lower cork content, up to 50% [1]. The second table gives the ranges.

Expanded cork is different again. The brochure says super-heated steam in an autoclave makes the granules expand and release a natural binder, their own suberin, so nothing is added [4]. Amorim lists expanded cork board as having low mechanical resistance [1]; ask whether that suits a board that must hold hanging weight.

In agglomerated products, the review reports higher compressive stiffness and plateau stress with a more rigid binder, a denser material or larger granules [3]. In some of the studies it summarises, the review reports a partial decrease in stiffness as binder amount increases, depending on the range investigated, and attributes this to the lower modulus normally possessed by the polymeric binder compared with cork [3]. Two boards that both look like cork can therefore feel different.

Amorim explains the mechanism simply: the air inside each cell is pushed into less space and the flexible walls return to their original shape [1]. A review of the compression literature describes three regions in the stress-strain curve: a linear elastic region, a plateau and then densification [3].

Recovery is high but not perfect. Two studies summarised in that review report an almost full recovery of dimensions after low deformations and a permanent deformation after larger ones, and both ascribe the recovery to the unfolding of the cell walls [3]. Amorim separately lists compressibility recovery above 70% for its agglomerated cylinders and blocks [1]. These are different measures and are not directly comparable.

One caution. These findings come from bulk compression tests, not from pushing a pin into a board. They help explain why a pin hole in cork can close up over time, but they do not promise that every hole will close or that every cork product behaves the same. The figures and mechanism are in our guide on why cork springs back.

The sheet size below is illustrative and is not a claim about any ArtzFolio product. The density ranges are Amorim's [1].

Sheet weight. Mass equals density times volume. For an illustrative sheet of 1 m x 1 m x 0.01 m (10 mm), the volume is 1 x 1 x 0.01 = 0.01 m3. At Amorim's agglomerated density range of 140 to 600 kg/m3 [1], it weighs 0.01 x 140 = 1.4 kg to 0.01 x 600 = 6.0 kg. At the 160 to 260 kg/m3 range Amorim gives for natural cork [1], it weighs 1.6 kg to 2.6 kg. A board's weight also depends on its other layers.

The spread in weight shows why density belongs in the specification, because two cork surfaces of the same size can differ several times in weight [1].

This guide describes the material, and it does not tell you which form of cork a given board uses. Ask that separately. Add these points to your frame or board order brief and compare answers against the boards buying guide.

1. Which form of cork is used: natural cork, agglomerated cork or another product, and the thickness of the cork layer.
2. For agglomerated cork, the density and the binder type, since the review reports that density and binder rigidity affect stiffness [3].
3. Which layers sit under the cork, such as the core and the back, because they carry the weight and the hanging load.
4. How the surface should be checked: pin a few sheets onto sample boards and look at the holes again after a few weeks. The review notes that cork specimens kept changing size for 15 to 20 days after testing in two studies [3], but those were not pin tests, so treat that as a reason to wait and not as a fixed timescale.
5. Any claim a supplier makes about origin or certification, asked for in writing with the document attached.

ArtzFolio is a private-label and OEM/ODM manufacturer in Noida that works with businesses and brands only. Our board range covers pin, cork, magnetic, white and glass boards. Quotes state price, minimum order and lead time, payment is 50% advance and the shipping term is EXW Noida. Enquiries get a reply within 1 business day. Share your board type, size and surface preference on the contact page, or read pricing, minimums and lead times to see how a quote is built.

1. Cork Solutions & Manufacturing Processes, Amorim Cork Solutions. amorimcorksolutions.com (read 2026-11-08)
2. The rationale behind cork properties: a review of structure and chemistry, BioResources (Pereira, H., 2015, vol. 10, no. 3). bioresources.cnr.ncsu.edu (read 2026-11-08)
3. The Compressive Behavior and Crashworthiness of Cork: A Review, Polymers 2022, 14(1), 134, published online 30 December 2021 (Sergi, C., Sarasini, F. and Tirillò, J.). pmc.ncbi.nlm.nih.gov (read 2026-11-08)
4. Expanded insulation corkboard brochure, Amorim Cork Solutions. amorimcorksolutions.com (read 2026-11-08)