An In-depth Look at Valve Oil

Introduction

The following article was originally posted on MusicChem.com. That site has now disappeared, but this article can still be found (unformatted) on NEMC. It is a serious dive into the properties of valve oil, and may be useful for people who revel in the complex minutiae of obsessive performance traits.

Quite a few of the oils mentioned here are no longer in production, and there are a few modern oils that are missed. Regardless, the points made are still highly informative.

Are all valve oils the same?

Valve oils for trumpets fall into 3 groups: Type 1 are the low technology formulations based on a modern day version of kerosene (the odor is quite obvious); Type 2 are high viscosity oils; and Type 3 are light weight oils with little or no petroleum odor.

There are so many trumpet oils available because there are so many businessmen who combine a little kitchen chemistry with a lot of advertising dollars to create a product; however, developing a functionally correct lubricant requires a thorough understanding of Material Science and Fluid Dynamics. Ignoring these principles has resulted in the proliferation of fundamentally poor valve oils. For example, one trumpet oil company that uses silicone oils is ignoring the hysteresis and build-up problems that plague silicones when used on sliding metal surfaces. In fact, a primary manufacturer of silicone – Dow Corning- specifically recommends against using silicone for sliding metal/metal lubrication. “Some oils gunk up valves.” We have all heard this misleading statement, but when we complete this presentation, you will have enough understanding to never again suffer from a “gunked up valve”. The statement, however, leads us into the main part of the subject: Speed and Endurance.

The primary purpose of valve oil is to provide a thin film of slippery fluid which clings to the valve and casing, thereby acting as a barrier to prevent direct metal to metal contact between these critical surfaces. A thick oil (Type 2) may be slippery and provide an excellent barrier, but it would cause the valves to be very slow. A thinner fluid (such as kerosene in Type 1) would be fast initially but its rapid evaporation would cause the valves to slow down quickly, and eventually stop moving altogether. Consequently, long ago we recognized that there are two major performance considerations in researching a new oil for piston valves: Speed and Endurance. To ignore either in favour of economy or naivete, is to guarantee disappointment for the musician.

Speed

The most important quality in a valve oil is its ability to promote speed by reducing friction, but the oil also causes some resistance of its own. This measured resistance is called viscosity, and the unit of measurement is centi-Stokes (cSt.). Musicians seeking a “thin” oil are simply looking for a low viscosity oil. Although you can get a rough idea about how viscous an oil is by applying some to an inclined surface and watching it run, the accurate way to measure viscosity is with capillary viscometers. Since actual viscosities of different oils have not heretofore been published, we have presented some in a table below. These oils were purchased from different stores.

Valve oil viscosity chart comparisons:

WATER – 0.00
MINERAL SPIRITS – 1.34
CLARK TERRY – 1.83
BENGE – 1.99
BLUE JUICE – 1.99
PLAYERS – 2.15
JUPITER – 2.20
ROCHE-THOMAS – 2.31
HOLTON – 2.38
HYBRID 141-A7 – 3.02
PRO-OIL RED – 3.61
SPACE FILLER II – 3.72
AL CASS – 3.73
PRO-OIL BLUE – 3.80
SPACE FILLER I – 5.10
SLIDE (for trombones) – 5.12
ALISYN – 7.59

As you can see, several valve oils are so “thin” that they approach the viscosity of water, while others are very viscous. Water has by far the lowest viscosity, but if low viscosity was the only criterion for speed, then the spit in your horn would be enough to keep your valves fast. The fingers of an experienced trumpet player can sense even the slightest valve hesitation, and this experience has shown that the optimum viscosity for speed lies somewhere in the 1.1 – 5.0 cSt range.

In developing HYBRID (our experimental reference standard for piston valves) we have discovered that the optimum viscosity for valves in good condition is in the 2.5 – 4.0 cSt. range; however, badly worn valves can tolerate or even benefit from somewhat higher viscosity oils. Nonetheless, viscosity isn’t the entire answer; speed means nothing if the action is not smooth, or if the valves become slow in the middle of a performance. A working musician cannot afford to even think about his valves during a performance. In other words, what about endurance?
In future correspondence we will discuss endurance, corrosion, the best technique for cleaning a trumpet, and why horns gunk up. We will stop here and await any questions from the list.

Endurance

Endurance is the oil’s ability to maintain the original fast and smooth valve action over many hours despite playing conditions. This characteristic is very difficult to develop in an oil without compromising speed because endurance is the end result of a complex series of interrelated properties and conditions: evaporation rate, film strength, surface tension, water solubility, and valve cleanliness.

Evaporation rate

When a valve oil evaporates so that less than 40% of the original oil remains on the valves, they will begin to hesitate in an unpredictable fashion. In more expensive horns with clean and very tight valves, the slowdown is much sooner and sudden seizing of a valve is common.

In the relative evaporation rate table below, we have listed the percent of oil remaining on a surface as a function of time at room temperature. The data does not suggest that a given valve oil will last the number of days shown, but rather the percentage of oil remaining after a given period of time. Compare the evaporation rates of the oils with their viscosities, and remember that Endurance is enjoying fast consistently smooth action for a long time – not slow action for a long time. Some trumpet oil manufacturers include a heavy oil in their formulation to slow down the apparent evaporation rate, and (hopefully) to make the oil last longer. Unfortunately, as evaporation occurs, the lighter oil content diminishes until only the slow heavy oil remains on the valves. Our experiments back in 1976 proved this.

Percent Remaining Versus Time (19 hrs 48 hrs 72 hrs 96 hrs 120 hrs)

WATER 1.00 – 0%
MINERAL SPIRITS 1.34 – 0%
CLARK TERRY 1.83 – 16% – 7% – 6% – 0%
BENGE 1.99 – 35% – 13% – 8% – 5% – 4%
BLUE JUICE 1.99 – 44% – 23% – 17% – 12% – 8%
PLAYERS 2.15 – 44% – 20% – 13% – 8% – 4%
JUPITER 2.20 – 33% – 17% – 15% – 13% – 10%
ROCHE-THOMAS 2.31 – 16% – 13% – 13% – 12% – 11%
HOLTON 2.38 – 25% – 7% – 4% – 0%
HYBRID 141-A7 3.02 – 92% – 75% – 64% – 55% – 46%
PRO-OIL RED 3.61 – 74% – 44% – 33% – 21% – 11%
AL CASS 3.73 – 75% – 48% – 37% – 26% – 16%
PRO-OIL BLUE 3.80 – 77% – 50% – 37% – 25% – 13%
SPACE FILLER I 5.10 – 100% – 100% – 100% – 100% – 100%
SLIDE (t-bones) 5.12 – 100% – 100% – 100% – 100% – 100%
ALISYN 7.59 – 100% – 100% – 100% – 100% – 100%

Endurance is very sensitive to the integrity of the oil film on the valve surfaces. As the piston slides down the valve casing it rubs against the oil film. This movement tends to rupture the film and allow direct metal/metal contact. In hyper-tight valve assemblies (i.e., Monette and Schilke) oil film rupture is potentially more frequent and disastrous. This is a purely mechanical phenomenon which can only be prevented with an oil having a high film strength.

Achieving a high film strength oil within the optimum viscosity range (2.5- 4.0 cSt) is quite difficult. Although it is not easy to measure this film strength directly, it is best understood through demonstration. Firstly, a high film strength will give a smooth, slippery feel when the oil is rubbed rapidly between the fingers. When shaken, an oil with a high film strength will yield bubbles that collapse within 1- 3 seconds. Whereas an oil with poor film strength will tend to entrap air for a much longer time. Oil film rupture can also occur for a different reason: moisture.

Water trapped in the valve chamber experiences the sheer force of the piston moving rapidly past the walls of the valve casing. This action tends to emulsify the trapped moisture into the oil. This micro emulsion not only has an elevated viscosity, but also displaces the oil from the valve surface. With the oil film thus compromised, the valve and casing easily rub against each other to produce friction, slowed action and wear. Therefore, in addition to the properties discussed above, for an oil to be truly effective it must also resist emulsion formation.

Sticking Valves

How many times have you heard, “My valves were slowing down, so I reoiled with a different oil and suddenly the valves stuck.” The tendency is to blame the oil, and although the oil played a part, other causes are more likely for this ‘Gunking Up’ phenomenon. Every note pushed through the horn is borne in the musician’s moist breath with the valve chamber acting as a trap for not only this moisture but the aerosols suspended in it. These aerosols contain enzymes, proteins, and salts. As long as the valve oil rejects this mixture, it will simply pass through the valve chamber, but as the oil boundary film becomes depleted or compromised, the moisture and its aerosols become attached to the metal.

When the musician reapplies oil to the moisture impacted valves (or to valves that had enough time for the spit to dry onto the metal) the oil will actually deposit on top of this layer. As this process is repeated, a series of sticky layers and high spots build up until the valves become sluggish or stick completely. There is no oil that can permanently protect against this “spit sandwich” but you can prevent it through effective cleaning and proper oiling.

Corrosion

A lesser know consideration in selecting a valve oil is corrosion. It is absolutely necessary to liberally coat the valve and casing surfaces so that excess oil will transfer to the internal solder joints. In doing so it will protect them against dezincification (red discolouration) and corrosion (blue-green discolouration) which are caused by exposing the naked metal to moisture. Monel valves will similarly be protected against spotting. An oil with low surface tension and a low viscosity will spread quickly and evenly, thereby coating these surfaces without fear of over-oiling. It is very difficult to properly coat a valve, the casing and the solder joints with a high viscosity oil. The topic of corrosion will be covered in depth at a later time. Players of rotary valved instruments will want to pay close attention to this article.

How to select your next bottle of piston valve oil:

A high speed oil is a thinner oil. If you don’t recall which oils are heavy, a quick test in a store is to apply a drop or two of each valve oil onto smooth surface (i.e. a clean mirror, a sheet of glass or a sheet of metal). Tilt the surface and see how fast the oils run down the sheet; heavy oils move slower and can be eliminated from the selection.
The oil should have a slow evaporation rate and remain slippery. A good evaporation test is to place some of the oil in the palm of your hand and feel how long it feels slippery relative to a different oil. Kerosene based oils are not desirable because they evaporate quickly. The presence of kerosene is apparent from its characteristic odour which will become evident in this test.
The film strength is crucial. Hold a group of well capped bottles of high speed oils in your hand, turn them upside down and shake them as a group for 5 seconds. Note how fast the foam breaks; the faster the better. Weed out the ones that have a slow foam break.
Water rejection is important. This is a test of how fast the water and oil separate but since it requires sacrificing some oil, a store owner might not want to do it. The test is to add equal amounts of water and the valve oil to a small container (a test tube or even an old bottle), and shake vigorously for 10 seconds. Observe how long it takes for the oil and water to separate almost completely.

Conclusion

Speed and Endurance in an oil are two different properties; experience will show that the best oil will not sacrifice one for the other. To quote a longtime friend of ours (Art Farmer), “I play very fast, and I have to concentrate on the music. I can’t afford to even think about my valves during a performance.” To develop an oil for horns built on better technology, one must employ better lubrication technology. Until now, no one has tried to enlighten either the musicians or store owners that there is a science to improving valve oil, and only a few valve oils take advantage of the science. Hopefully the results of our research brought out in this article will dispel the mystique of valve oils, and make oil selection almost bulletproof.