What is MDF?
Medium-density fibreboard (MDF) is an engineered wood product formed by breaking down hardwood or softwood residuals into wood fibres, combining it with wax and a resin binder, and forming panels by applying high temperature and pressure. It is stronger and much more dense than chipboard. 
Typically, in the UK, this material is used in a wide variety of applications across the construction industry. The stability and cost of MDF makes it ideal for painted applications like skirting board, stair risers, window boards, architraves and some furniture. It can also be faced with a thin layer of solid timber, called a veneer, which allows it to be used for in applications where a high quality timber finish is required, with lower budget and high stability requirements.
The major issue with MDF is that it has a tendency to swell if exposed to moisture, which can ruin the finish. With the introduction of moisture-resistant MDF, always identifiable by its green colour, this problem was reduced.
What is Medite Tricoya?
Medite Tricoya is a new particle board. This material is currently made by the same process as regular MDF, but by using Accoya as a starting material. Accoya is a treated softwood, which offers superior stability, moisture resistance and longevity compared to all species of solid timber; we regularly use this product in high specification external joinery, particularly in the London-market.
The Test
We are very proud of our craft at Gowercroft. We actively seek out raw and processed materials which can help us deliver the highest quality products possible, and also give the highest value proposition to our customers. This involves going through rigourous testing to ensure that the new materials out-perform existing.
In this vein, we wanted to see whether Medite Tricoya’s reputed stability in contact with water was justified and do a direct comparison against standard MDF and moisture-resistant MDF. We began by accurately measuring the sizes of a small block of each material with use of a micrometre; these instruments are accurate beyond 0.1mm. The three samples were then submerged in room temperature water for 36 hours, removed from the water and remeasured. Expansion was recorded, before the samples were cut in half to reveal the core of the timber blocks, and to indicate the water penetration into the sample. Finally, the samples were allowed to dry over 24 hours, before being remeasured to see whether expansion/damage was lasting.
Results
The test showed that Medite Tricoya was a far more stable material when submerged in water, swelling only 3.4% in thickness, compared to 11.1% for regular MDF and 16.7% for moisture-resistant MDF. The difference in swelling between the regular MDF and the moisture-resistant MDF was considerable and presents an anomaly against expected results. It is likely that the process undertaken to make the MDF resist moisture does not have a positive impact on the materials soak resistance.
In all three samples the swelling in height and width of the samples was relatively small at between 0.2% and 0.6%, again Tricoya showed the lowest available expansion percentage.
When the samples were cut in half, all three were moist in the core, suggesting that none of the materials prevented water absorption.
After drying time, there was a clear reduction in the swelling of the samples. This shrinkage was relatively uniform on the sample of Medite Tricoya, where the end thickness was between 0.9% and 1.6% larger than the original sample. With the standard MDF, the thickness ranged from 3.9% to 10.6% expansion; and the moisture-resistant MDF sample ranged in end thickness from 5.9% to 16.3%.
The samples of standard MDF and moisture-resistant MDF split and cracked, with fissures forming on the corners and emanating towards the centre of the samples (as can be seen in the images below). These disappeared after full contraction of the sample, but will no doubt undermine the strength of the material in the longer term. There was no such cracking seen in the Medite Tricoya sample.
In Summary
Medite Tricoya is clearly the most moisture-resistant product of the three tested; it absorbs the least water, swells least in contact with water, returns most closely to original size when dried out, and shows the least degradation of the structural integrity during drying.
When protected with a high quality, factory finished paint system, we would be comfortable recommending Medite Tricoya for high-specification, exposed and external applications. We are currently manufacturing external doors for a prestigious property in Kensington, London with Tricoya panels, which can be seen above. A full case study will follow.
Full Results
Original sizes:
Standard MDF; width 49.8mm, height 49.8mm, thickness 18.0mm.
Moisture Resistant MDF; width 49.8mm, height 49.8mm, thickness 18.0mm.
Medite Tricoya; width 50.9mm, height 50.1mm, thickness 14.8mm.
Sizes (after 36 hours submerged):
Standard MDF; width 50.0mm, height 50.0mm, thickness 20.0mm.
Moisture Resistant MDF; width 49.9mm, height 50.1mm, thickness 21.0mm.
Medite Tricoya; width 51.0mm, height 50.3mm, thickness 15.3mm.
Percentage Changes (after 36 hours submerged):
Standard MDF; width +0.4%, height +0.4%, thickness +11.1%.
Moisture Resistant MDF; width +0.2%, height +0.6%, thickness +16.7%.
Medite Tricoya; width +0.2%, height +0.4%, thickness +3.4%}.
Final Sizes (after 36 hours submerged, and 24 hours to dry):
Standard MDF; thickness range 18.70mm to 19.90mm, expansion percentage +3.9% to +10.6%.
Moisture Resistant MDF; thickness range 19.06mm to 20.93mm, expansion percentage +5.9% to +16.3%.
Medite Tricoya; thickness range 14.93mm to 15.03mm, expansion percentage +0.9% to +1.6%.