There is good reason why the words COLD and STEEL go together so well. Steel is the one metal that we associate with being cold and hard. Joni Mitchell sings of “Cold Blue Steel and Sweet Fire” (released on the album, “For the Roses”, 1972). But we use other terms for metals to help us describe the world; “hard as iron” and “bold as brass” come to mind and to this we might now add “kind as Salox”. Why is this?
Steel feels cold because compared to many materials it transfers heat from your body fairly quickly – so-called “thermal shock”. The problem is that all the while it is doing this, you feel the cold sensation in your hand (or mouth!). Salox† transfers heat from the body up to 8 times more rapidly than steel so why do we think horses accept it more readily than steel?
Research on human subjects in 2006 (for those with access to the scientific literature see: Ploner et. al. J. Neuroscience, 26, 10879, 2006) showed that reaction times to pain applied in a sudden impulse lie between 300 and 500 milliseconds (0.3 to 0.5 seconds). A metal mouthpiece that remains significantly colder than the body for much longer than this will likely produce an aversionary response. Your horse will try to avoid the feel of the cold steel. This is the bitting equivalent of the so-called 'cold backed' horse who has become behaviourally conditioned to stiffen against the anticipation of the discomfort of an ill-fitting saddle. However, if the metal mouthpiece reaches body temperature much more quickly, and crucially if this is fast enough, the time taken to sense the mouthpiece temperature may be comparable to the heat-up time of the metal. In other words, by the time the sensory information has reached the brain the bit has warmed up and the horse decides that nothing need be done to avoid it.
But objects can also feel warm for the opposite reason. As we describe in the next section, if the thermal conductivity is very low and the heat capacity and/or density are high the heating and cooling rates are very slow and the body has time to slowly adjust to the temperature differences. This explains why plastic horse bits will feel warm in your hand even though they may have a very different temperature. Read on...
What material properties determine heating rate?
The answer is that it is a combination of three properties, thermal conductivity (l), density (r) and specific heat capacity (Cp). For any object of a defined size and shape we can say that heat transfer rate is determined by the ratio; l/r.Cp. Faster heat transfer occurs when l is high and both r and Cp are low. This ratio (the thermal diffusivity) is calculated for the materials we have discussed above and is presented in the table below*.
Transferring this information into the rate of heating, the following graph shows the heating rate of a selection of metal bit mouthpiece materials*. Clearly the temperature of Salox† rises by far and away the fastest and we believe that this high rate of heating exceeds, or is comparable to, the reaction time of the equine nervous system. A comfortable temperature is reached almost before the horse makes a cognitive reaction to the change.
* Thermal conductivity of Salox measured to be 118 W/m.K (+/- 5 W/m.K) at the University of Durham, UK, using the method described in R.A. Fairs, Phys. Edu., 23, 378 - 379, (1988). Values for german silver, stainless steel and titanium alloy are calculated using literature data. "Plastic" refers to polypropylene as a typical polymer example.
Taste: what do we know?
Answer this question: “What does chocolate taste like?” Actually therein lies the problem here; what can we measure about the taste of anything and how do we explain the chocolate experience to each other? Science has defined four basic taste types; Sour, Sweet ,Salt and Bitter, that in combination, produce all the various tastes we sense. This is similar to the mixing of the primary colours, (for example, red, yellow and blue) to create subtle shades across the whole spectrum.
The idea that metals can be sweet is not new. Victorian charlatans added lead salts to bread when sugar was scarce and cases of lead poisoning of children licking lead salt-based paint (containing lead carbonate) were well known in the early part of the last century before lead-based paint was banned.
But, note what we just said: Lead salts are sweet - what do we mean? A 'salt' in this context means that the metal is in its ionic state (positively charged) and is available in this form for binding to the sensory receptors (taste buds) on the upper surfaces of the tongue. The lead metal on its own (not charged) is unable to bind to the taste buds so it would have to be converted to its ionic form to be detected as a sweet taste.
This brings us to that mysterious material, “Sweet Iron”. This metal, a form of iron containing a small amount of carbon, was found to be favoured by horses. Sweet Iron rusts readily, turning the iron into iron oxides; salts of iron. These salts then are responsible for imparting flavour to the metal.
Metals such as copper were later introduced into horse bit mouthpieces with the hypothesis that horses would enjoy the flavor that this imparts and once again, this appears to be the case for some horses. Once again however, copper metal needs to be in its ionic form, as the salt, copper oxide. The oxides of copper makes this metal available for sensory reception by the taste buds by changing to the slightly different forms of copper hydroxide; Cu(OH)2 and Cu(OH). These two types reflect the multivalent (different values of positive charge on the copper) states of copper and, as we show below, there are large differences in the solubility between the two.
In saliva, it is the solubility of these metal hydroxides that is perhaps the one measurable property that we are looking for. Saliva is an electrolyte, containing dissolved ions (carbonates, phosphates etc.) and although it has a pH of around 7 and is therefore neither acidic nor basic, pH conditions in the mouth can vary depending on a number of factors such as whether food residue is present or whether lactic acid is present. With this in mind, the table below‡ shows a value known as the 'solubility product' of hydroxides of metals in water (pH7) and provides an approach to answering our question on taste.
Although these numbers may not be familiar, what they tell us is that iron (III) (ferric) hydroxide (on the far right) is nearly insoluble compared to the corresponding iron (II) (ferrous) hydroxide, on the far left. Cu(II) (cupric) hydroxide is 1 000 times less soluble than ferrous hydroxide. The more soluble hydroxides (Iron and Zinc) are therefore likely to be those that are available for receptor binding on the horse's tongue.
Isn't salivation the key?
We should just touch on salivation here, after all, Pavlov showed that dogs could associate with food by observing them salivate at the ringing of a bell. We make an assumption that salivation shows us that the horse is enjoying the taste of a bit and while we all know that a crunchy apple leads to a happy mouthed horse, the question over what is going on with salivation during riding remains open. We've been reading up on Hilary Clayton's work at Michigan State University and her study on salivation ( "Effects of different bits and bridles on frequency of induced swallowing in cantering horses", Equine and Comparative Exercise Physiology, 2(4); 241–244, 2005). This focused only on whether horses were restricted in their swallowing during performance riding and did not make a direct assumption about the taste of the mouthpiece, only that the mouthpiece might encourage salivation through a 'parasympathetic' nervous system response. It is too much of a leap to invoke taste as the sole trigger for this response. Horses that are comfortable may well be producing extra saliva - but, ridden without restriction and therefore swallowing this excess, may well not show it at the mouth.
What do we mean by "Oxidation" and why is it beneficial?
Oxidation naturally forms on the surfaces of metals, except, at normal temperatures, for gold and platinum and some others. Brown rust on sweet iron bits or the colourless protective chromium (III) oxide layer (Cr2O3) on stainless steel bits are both examples of surface oxidation. In Salox the surface layer comprises a mixture of oxides. The copper and zinc oxides are the more soluble among them but we have taken advantage of colourless and nearly insoluble (see table above) aluminium oxide (alumina, Al2O3) to restrict the amount of soluble oxides that your horse will ingest when using the product. Aluminium oxide helps to trap the more soluble salts inside the mouthpiece and limits the oxidation of these components††. In this way we help to minimise the amount of unintentional feeding of metal ion nutrients. As an additional bonus, the mouthpiece remains relatively free of coloured oxides which helps to reduce tarnishing.
†† For more detail: M.D. Sanderson and J.C. Scully, "The high temperature oxidation of some oxidation-resistant Copper-based alloys", Oxidation of Metals, 3, 59 - 90, (1971)
The Engineering Process
Revolutionising the art of the Loriner
Computer Aided Design technology has made it possible for Neue Schule to be much more innovative when creating new mouthpieces and cheeks. This new state-of-the-art technology now allows our design team to precisely and proportionally reproduce the required ergonomic shapes and details in any mouthpeice size. It enables us to match design to equine mouth conformation; profiling and engineering critical design features to fit comfortably within the tight parameters and sensitive areas of the mouth. This utilises the connection points necessary in order to promote effective communication through the rein between rider and horse.
Neue Schule designer bits promote the comfort and consequent performance of the horse. The variance in mouth conformation between breeds has been studied in detail. The various designs accommodate, for instance, large tongues, fleshy lips, thin angular bars or general oversensitivity. CAD enables us to create a precision tool that, in the right hands, subtly utilizes the specific pressure points necessary to promote a particular way of going or eradicate an unwanted bitting evasion owing to discomfort. Even when the hands aren't perfect the attention we pay to mouth conformation in the design softens the impact and helps develop the rider/horse relationship.
Without CAD technology and modern manufacturing techniques we could not have achieved the degree of precision necessary to achieve these advances.
Let's look at one example: The Verbindend
This smoothly contoured mouthpiece creates a channel for the tongue to lie in causing the horse to soften & relax through the jaw. This then greatly emphasises the signals through the rein. It allows one to lighten the forehand, lifting the shoulder thus promoting self carriage and the ‘throughness’ needed for sustained advanced movements. It also enhances the bend for lateral work & voltes (smaller circles) etc.
When the rein is taken up this bit cleverly connects using several communication points within the mouth. The action of the angled lozenge plays a part in this. For instance when a contact is taken the lozenge rotates and applies slightly more pressure across the tongue's centre, where it is thicker and not as sensitive. Simultaneously pressure is reduced over the tongue’s thinner, more sensitive, outer edges. Before CAD it was not possible to obtain these critical profiles and angles and reproduce them in any size or thickness without losing the integrity of the design and subsequent action of the bit.
Although the correct design of the bit is critical another extremely important factor is the material and huge strides have been made in this area. Neue Schule has identified a property of metals, the thermal diffusivity, that it believes to be important for the comfort and acceptance of the bit..
Neue Schule Salox Gold* is our unique metal that rapidly equilibrates to blood temperature so that the mouthpiece is less likely to feel like a foreign body in the horse’s mouth. If this happens we can expect a more relaxed acceptance of the bit which would promote responsiveness to the rider’s aids and culminate in a soft, consistent contact.
Our large equestrian retail store In Newton Abbot Devon is open Monday-Saturday 9.30am-5.00pm Our team are always happy to answer any questions and are available on 01626 204099 or by email at email@example.com