Armadillo Merino® next to skin merino wool clothing for for extreme users and conditions.

Why Armadillo Merino for FR, no-melt and drip burn protection and more.

Over the coming weeks I will touch on some of the key performance attributes of Armadillo Merino®.  The first in this series is Protection. At a later date I will also talk about each of the specific attributes in separate posts, but that is more detail than is required here as we start to talk about the key attributes of Armadillo Merino®.

1. Armadillo Merino® Protection: No Melt - No Drip & Natural fire resistance

For first responders, police, military and fire fighters the next-to-skin is the last line of defense against heat and flames. For this reason, special consideration should be given the correct next-to-skin garments. In a lot of situations a protective FR coverall or suit will be worn as the first main line of protection against heat or flames. In the case of FR coveralls these work exceptionally well at protecting the user from flames, but unfortunately offer little resistance from heat. In a burn situation there are two elements, flame and heat. Most users think of the flames first, but then forget about the heat that conducts through the protective outer layer.

When speaking to wearers of FR coveralls and fire fighting bunker suits, they very quickly understand the heat element, but then I ask what base layer they are wearing. More often then not, it is a synthetic garment that can melt at as low temperature as 150°C (wool chars at 570°C as a comparison).

Why, I ask, and often they have not put the heat and melt elements together or they were influenced by slick marketing, not knowing the danger they were placing themselves in from melt and drip burns from their synthetic next-to-skin garments. 

Another consideration for users who wear FR coveralls is what is on top of the overalls. We recently spoke to one user who had FR coveralls on and padding on top of this again, but flammable liquids dripped down between the FR coveralls and the padding, and then caught fire. He was fortunate, as he was in a training situation, and was able to strip the padding off and smoother the flames and heat, although he did say his knee got pretty warm in the meantime.

So what is the solution?

We recommend merino wool base layer, specifically Armadillo Merino®.

See our Police and Fire Fighter Collections 

Armadillo Merino® fibre has naturally occurring flame resistant properties that make it suitable for use in base layer clothing. This flame retardant properties are due to its unique chemical structure (a high nitrogen content (14%) combined with a high relative moisture content), which displays the following beneficial properties:

  • A very high ignition temperature (570-600°C)
  • Doesn’t melt or stick upon burning, rather, it forms an insulating char
  • Self extinguishing
  • A high Limiting Oxygen Index (20- 25%) – with the LOI being a measure of the minimum % of oxygen required to sustain combustion
  • A low heat of combustion
  • A low rate of heat release
  • Evolution of less smoke and toxic gases than formed during combustion of most synthetic fibres

A comparison of Merino fibre with other important textile fibres, demonstrates superior performance across virtually all parameters measured.

FR Index

Another advantage of merino wool is that it offers some thermo protection from heat from the outside. In the same way that merino wool helps to keep you warm when it is cold, it also helps to keep some of the heat out. This is particularly important when using FR overalls, as they stop the flame, but not much of the heat. Adding a merino base layer under the FR coveralls, can significantly increase the user comfort and protection. 

To learn more about the natural No Melt, No Drip properties, see our whitepaper.

Download our No Melt - No Drip Technical Paper Sun 1600 x 500.png

2. Armadillo Merino® Protection: SPF40+

The second key element to protection, is protection from the sun. 

Ultraviolet (UV) radiation is a component of the solar radiation that comes from our sun.  The potential for a fabric to protect its wearer from ultraviolet radiation is described as its Solar or Ultraviolet Protection Factor (SPF or UPF). UPF relates to the time taken before human skin begins to redden after exposure to ultraviolet light – and is usually measured on a scale of 0-50.

The greater the amount of radiation able to pass through a textile the lower the UPF. The most important of the factors influencing UPF are summarised below:

 Fibre type (wool typically has a much higher UPF than synthetic fibres).

  • Fabric density (denser structures confer a higher UPF).
  • Degree of stretch (with the UPF being lowered in a stretched state).
  • Fabric colour (with the UPF factor dependent on the amount of dyestuff present and the chemistry of the dye itself – darker colours usually result in a higher level of protection).
  • Whether the fabric is wet or dry (UPF decreases markedly when wet).
  • Presence of UV absorbing finishes and/or optical brightening agents
  • Garment design

Research has shown that wool absorbs radiation throughout the entire UV spectrum, whereas untreated cotton, nylon, acrylic, and silk are poor absorbers of UV. Due to this, Armadillo Merino® has a UPF of greater than 40.

 SPF index - Armadillo Merino® 40+
UPF Factor for Summer fabrics (mean weight 158 g/m2)

To learn more about the natural UV protection, see our whitepaper.

Download UV Protection Technical Paper

3. Armadillo Merino® Protection: Acid Resistance

Unlike many synthetic fibres (e.g. nylon, rayon etc.) and cotton, merino fibre demonstrates very a high resistance to acids. In fact, many of the wet treatments imparted to merino fibre and fabric (dyeing, shrink-resist and flame resist treatments) rely on exposing merino fibre to low pH in order to lock such agents within the fibre and achieve very high levels of fastness.

4. Armadillo Merino® Protection: Chemical Residues and Aerosol Penetration

Because of its unique internal and surface chemistry (in particular, its hydrophobic cuticular scale structure) wool fabrics have been shown to be more resistant to penetration of aerosols such as insecticides etc. than those made from synthetic fibres such as nylon, acrylic and rayon. 


In conclusion, we believe there is no place for synthetic base layers that can melt or drip in the first responder environment. Often the user is unaware until it is too late the of the risk they are exposing themselves to when wearing the “wicking” synthetic baselayer. (I will talk more at a later date about wicking vs. breathing. Merino wool is breathable, which in all tests out performs wicking.).

Further synthetic base layers have:
- limited UV protection
- limited heat protection
- limited acid protection
- they smell, or are treated with heavy chemicals to stop the smell

When you consider all of the above, the case just keeps getting stronger for merino wool as the best option for first responders next-to-skin and last line of defense.

If you are interested in more, see "Is it time that Police consider the base layer as their last line of defense"

Or you can always visit our shop.

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Topics: Military, Fire Service, Police, Merino Wool Knowledge

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