Colored smoke is composed of an aerosol of tiny particles that is vaporized or combusted. A specific pigment or dye in the aerosol influences the color of the smoke, and the mixture generally consists of a cool-burning formulation with lactose, potassium chlorate oxidizer, or dextrin as the fuel. Single or multiple dyes are then added to an amount equal of about half of the mixture, and a small amount of sodium bicarbonate is used as a coolant.
The mixture in the smoke grenades used in a paintball match is called cool or cold burning. In this case, no external flame is generated, and the cartridge temperature is lower when compared to military distress smokes that burn at elevated temperatures. As the smoke grenade mixture is burnt without atmospheric oxygen, it can even burn underwater.
The different colours are produced by using the following composites:
- Violet: Solvent Violet 13 (C21H15NO3)
- Green: Quinizarine Green SS (C28H22N2O2)
- Orange: Sudan I (C16H12N2O)
- Blue: Victoria Blue BO (C33H41N3O – hydroxide)
- Yellow: Aniline Yellow (C6H5N=NC6H4NH2)
- Red: Sudan IV (C24H20N4O).
The Royal Air Force Aerobatic Team or ‘Red Arrows’ regularly use a specifically formulated liquid dye and an oil, which does not contain any chlorinated solvents (Figure 1).
Components such as tetrachloroethylene or trichloroethylene, dye and diesel oil are found in the colored smoke discharged from an aircraft. The diesel injected into the hot exhaust released from the jet engine reaches higher temperatures of more than 400°C.
Once released, the mixture is vaporized immediately and the resulting vapor is subsequently mixed with the dye to produce the respective colors. Otherwise, the vaporized mixture would be white in color. The buttons provided in the control column of the aircraft enable the pilot to initiate the smoke release.
Figure 1. The Royal Air Force Aerobatic Team or ‘Red Arrows’, commonly use an oil that does not include harmful chlorinated solvents along with a specifically prepared liquid dye.
If the smoke was generated through combustion, it would be hazardous for use in aircraft due to the risk of explosion. Therefore, testing the oils and dyes before the performance is required to eliminate any risk posed for the pilot, due to contamination of the oil or dye by highly combustible elements.
Also, the safety of the spectators watching at 1500 ft or below can be secured, by making sure that the amount of harmful solvents in the mixture is not high. The environmental impact of these oils and dyes should be taken into account as a key quality control aspect.
The Pearl™ Liquid Transmission Accessory is optimal for the analysis of these oils. When compared to the Quest™ ATR accessory, which is a highly appropriate accessory to perform the ATR infrared (IR) spectroscopic analysis of various liquid and solid samples and paints, the Pearl™ facilitates IR transmission spectroscopic analysis and not ATR.
It is also evident that the Pearl™ provides a higher spectral resolution, even in the case of samples that weakly absorb the IR light. Yet, the Quest™ is highly reliable as it can test samples of any consistency with high precision and requires minimal time for sample preparation.
The IR spectra obtained from Castrol LM grease at the region of 3500–600 cm-1 recorded by using both the Pearl™ and the Quest™ accessories is depicted in Figure 2.
As displayed the Pearl™ has a resolution that is 10 times stronger and displays the absorption strengths of the samples in a highly detailed manner.
Figure 2. Castrol LM grease spectrum, Pearl vs Quest
The Specac Pearl liquid transmission analysis accessory is an ideal tool to ensure the safety and the correct color of the smoke for an aircraft performing aerial acrobatics.
This information has been sourced, reviewed and adapted from materials provided by Specac.
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