[Chemistry] What makes a cream latherable (usable with a brush), and must it be non-transparent?
- Thread starter sg.
- Start date
1. Surfactants: soap (e.g. potassium palmate) and/or detergent (e.g. sodium lauryl sulfate).
2. If it appears transparent, it’s not lather. A single soap bubble is transparent, but the light going through a large/countless number of soap bubbles (i.e. foam/lather) will scatter, making the lather appear white. Even the use of something like a translucent soap bar, or clear shampoo will give white-appearing lather (for the same reason, i.e. light scatter).
2. If it appears transparent, it’s not lather. A single soap bubble is transparent, but the light going through a large/countless number of soap bubbles (i.e. foam/lather) will scatter, making the lather appear white. Even the use of something like a translucent soap bar, or clear shampoo will give white-appearing lather (for the same reason, i.e. light scatter).
Why is shaving gel not lather-able by a brush in the same way, yet it foams?
If a gel contains surfactant (many do), it will, to one extent or another, foam.
Typically, a can of foaming gel contains surfactant and propellant (e.g. butane). As the propellant exits, it vaporizes, causing the product to foam; often, the gel product at this stage is partially foamed, and further foaming (aeration) may be achieved via manual agitation.
Typically, a can of foaming gel contains surfactant and propellant (e.g. butane). As the propellant exits, it vaporizes, causing the product to foam; often, the gel product at this stage is partially foamed, and further foaming (aeration) may be achieved via manual agitation.
Strictly speaking the product expelled from an aerosol gel can does not contain propellant. The propellant (ie the pressurised gas gas forcing the gel from the can) never actually leaves the can. Gel cans are bicompartmental and the propellant (generally referred to as the "drive gas") - typically a blend of isobutane and propane - is in one compartment with the gel in the other. The gel is an emulsion containing a lower pressure hydrocarbon gas blend (the "blowing agent") - typically a mix of isobutane and isopentane - which "boils" when the gel leaves the can causing the gel to foam.
Butane unblended with other hydrocarbons has too low a pressure to be a propellant for shave foam or drive gas for shave gel. It has too high a pressure to be the blowing agent.
Indeed, the gaseous propellant typically is in a separate compartment. Was referring to the liquified (emulsified) propellant associated with the concentrate exiting. Thanks for clarifying.
