One product across a cabin is a decision, not an efficiency

Within arm’s reach in a business jet cabin you have aniline or semi-aniline leather, wool carpet, wood veneer under a polyester or polyurethane finish, stretched acrylic windows, polycarbonate, and plated brightwork. Their chemical tolerances do not overlap. Using one product across all of them is a decision to accept damage on some of them, whether or not anyone made it consciously.

This is the least glamorous thing on this site and it is the thing that separates a crew that has been trained from a crew that has been hired.

Leather wants acid, and gets destroyed by alkali

Leather is naturally acidic. The Canadian Conservation Institute, a government conservation body with no product to sell, states that leathers are naturally acidic in nature and that alkaline products such as saddle soap are harmful to them.

The Leather Institute’s care guidance is more specific for finished and semi-aniline leather: use a leather cleaner with a pH of 4 to 6. Its list of what never to use is worth reading twice: any high pH cleaner, cleaners containing alcohol, cleaners containing butyl cellosolve, any strong solvent, saddle soap, and mink oil. Those may cause cracking or other damage to the leather surface.

The distinction between leather types matters as well. Aniline leather is dyed with transparent colors only and has no topcoat, so it is porous and will absorb what is spilled on it. Semi-aniline has a color coat and a clear topcoat over it, so the topcoat is what you are cleaning and what you can destroy. An aviation tanner’s own care guidance for pigmented leather puts it bluntly: anything with a solvent base will solubilize the finish and damage the leather, and do not use acetone or bleach based products.

Wool is the opposite problem

Cabin carpet in this class of aircraft is usually wool, and Gulfstream’s own completion center handbook confirms it in capitals for its aircraft: carpet fibre content is 100 percent wool.

Wool is a protein fibre and alkaline conditions damage it. Research from wool processing literature puts the threshold plainly: alkaline conditions are far more damaging to the fibre, and above pH 9.5 will cause yellowing and damage to the fibre.

So the leather in a seat and the carpet under it want products at opposite ends of the scale, and the product that is wrong for each of them is the same product: something strongly alkaline, which is exactly what a general-purpose degreaser is.

Two more wool cautions, both from the same Gulfstream handbook and both about moisture rather than chemistry. Wet carpet may cause severe corrosion to aircraft flooring and structure. And do not sun dry or heat dry the carpet. Those two together are why carpet work in an aircraft is a different job from carpet work in a building.

Acrylic and polycarbonate fail differently, and both fail

This is where the most expensive mistakes happen, because transparencies are costly and the damage is not repairable.

Acrylic crazes. FAA AC 43.13-1B is explicit on transparent plastics: do not use gasoline, alcohol, benzene, acetone, carbon tetrachloride, fire extinguisher or de-icing fluids, lacquer thinners, or window cleaning sprays, because these will soften the plastic and cause crazing. Window cleaning sprays. The blue bottle in every hangar in America.

The acrylic manufacturer says the same and adds the important nuance: the material is subject to crazing, cracking or discoloration on contact with incompatible materials, and permitted cleaning includes isopropyl alcohol diluted to 30 percent strength. Diluted. Not neat.

The reason the stress matters is in the test method itself. ASTM F484 tests crazing on acrylic that is under bending stress, and stretched acrylic is tested unannealed, because a chemical that is harmless on a relaxed coupon can craze a window that is under load. A cabin window is under load.

The FAA’s own disinfection bulletin adds: ethyl alcohol based disinfectants can cause crazing on windows and window dust covers and can damage thermoplastics.

Polycarbonate has a different enemy. SABIC’s guidance for its polycarbonate sheet says never use abrasive or highly alkaline cleaner, and never use aromatic or halogenated solvents like toluene, benzene, gasoline, acetone or carbon tetrachloride. Alkalinity is on the acrylic list only weakly and on the polycarbonate list emphatically.

So a cleaner that is tolerable on an acrylic window can attack a polycarbonate one, and the two are not always distinguishable by looking.

Veneer and plated trim

Here the published data thins out, and we will not invent numbers we cannot support. What is documented is instructive anyway.

Gulfstream’s handbook says of wood finishes that polishes with a silicone base, such as the common household furniture polish, are not designed for this type of finish. Silicone is a problem for the same reason it is a problem on an exterior: it interferes with anything that has to be refinished later.

On plated metal trim, the same handbook specifies warm soapy water, prohibits abrasive cleaners and ammoniated detergent, and instructs carefully wiping down and drying all plated surfaces that may have come into contact with any sort of moisture.

Ammoniated detergent is, again, the blue bottle.

What a competent process actually looks like

Not heroic. Just deliberate.

• A short list of products, each matched to a material class, with the pairing written into the procedure rather than decided at the aircraft.
• Dilution measured rather than judged, because the clearance a product has is for the dilution it was tested at.
• Separate media per material class, so a towel that touched a cleaner is not going near a window.
• Test in an inconspicuous area first. Gulfstream says it in capitals for leather and it is right for every material in the cabin.
• The person doing it trained on that specific material, with the training recorded and current.

That last one is why we built our training into the platform rather than leaving it to experience. Experience means somebody has done it a lot. It does not mean somebody has done it correctly a lot.

The single most useful instruction

If you take one thing from this: keep general-purpose glass cleaner out of the cabin. It is ammoniated, it is on the FAA’s list of things that craze transparent plastics, and it is prohibited by name on plated trim in at least one airframer’s own handbook. It is also the product most likely to be in a hangar cabinet and to look completely harmless.

Everything else is a matter of matching a product to a material, which is what the interior service is, and what the method exists to make repeatable.