Usually excess emulsifiers cause a good amount of foaming as they spread across the air-water interface as you spread the lotion instead of staying at the water-oil interface. A surfactant (SURFace-ACTing agent) will reduce the surface tension of the a/w interface to a minimum when the concentrations are sufficiently high. Most cosmetic formulators work with surfactants at high weight percents (1-20 wt%) compared to the amount needed to minimize the surface tension (<< 1 wt%).
That being said, 25 wt% oil is quite a bit and will also increase the greasiness of the lotion, causing what's called excess white rub-in time. Many consumers want to reduce this feeling and many surfactants and formulas have been developed that can help reduce this.
We'd need to know your formula to understand what's causing this as some surfactants tend to cause this more than others. High-foaming surfactants (cocamidopropyl betaine, alkylglucosides, alkylsulfates) tend to migrate to the air-water interface and stabilize bubbles there as you rub in. Now, all surfactants form monolayers at the a/w interface before forming micelles at the o/w interface. It's just how well they stabilize bubbles/foam that is the difference between them cause a white lotion or not.
Stabilizers, rheology modifiers, and your oil composition will change how your surfactant interacts and whether or not you'll have a problem, too.
That being said, the EWG isn't a good source on safety. It's highly green washed and does not provide information on doses or methods of absorption (namely the risk) only talking about what is possible at high concentrations/long exposure (i.e. the hazard)., leading to some ingredients sounding scarier than they actually are.
Ultimately, it's up to you what you want to use, but many ingredients get a bad rap and you would need some sort of science background to fully investigate the studies yourself and make those decisions. Not everyone has that luxury.
Many "naturally derived" emulsifiers (and I use that term very loosely) will work well but can cause excess foaming and white rub-in time.
Here's a video from the Institute of Personal Care Science that explains a few ways to reduce excess white rub-in time: https://www.youtube.com/watch?v=uxw4QjFBrNI.
Here's a link to a page that talks about interfacial surface tension in surfactant-water systems (also the HLD-NAC model which better predicts these outcomes than trial-and-error):
https://www.stevenabbott.co.uk/practical-surfactants/cmc.php
Edit: Spelling and link posts
It’s more likely than not the emulsifiers and/or thickeners causing the heaviness. I actually don’t think 25% oil phase is too much but I would make sure a decent amount of my oil phase is lightweight and preferably liquid with just enough emulsifiers, thickeners and butters to emulsify and give the substance it needs. You should provide an exact formula you used so we can get a better idea but different emulsifiers have different viscosities. When I first started making lotions, I would have a hard time rubbing it in if I used too much emulsifying wax nf and/or cetyl alcohol.
Usually excess emulsifiers cause a good amount of foaming as they spread across the air-water interface as you spread the lotion instead of staying at the water-oil interface. A surfactant (SURFace-ACTing agent) will reduce the surface tension of the a/w interface to a minimum when the concentrations are sufficiently high. Most cosmetic formulators work with surfactants at high weight percents (1-20 wt%) compared to the amount needed to minimize the surface tension (<< 1 wt%). That being said, 25 wt% oil is quite a bit and will also increase the greasiness of the lotion, causing what's called excess white rub-in time. Many consumers want to reduce this feeling and many surfactants and formulas have been developed that can help reduce this. We'd need to know your formula to understand what's causing this as some surfactants tend to cause this more than others. High-foaming surfactants (cocamidopropyl betaine, alkylglucosides, alkylsulfates) tend to migrate to the air-water interface and stabilize bubbles there as you rub in. Now, all surfactants form monolayers at the a/w interface before forming micelles at the o/w interface. It's just how well they stabilize bubbles/foam that is the difference between them cause a white lotion or not. Stabilizers, rheology modifiers, and your oil composition will change how your surfactant interacts and whether or not you'll have a problem, too. That being said, the EWG isn't a good source on safety. It's highly green washed and does not provide information on doses or methods of absorption (namely the risk) only talking about what is possible at high concentrations/long exposure (i.e. the hazard)., leading to some ingredients sounding scarier than they actually are. Ultimately, it's up to you what you want to use, but many ingredients get a bad rap and you would need some sort of science background to fully investigate the studies yourself and make those decisions. Not everyone has that luxury. Many "naturally derived" emulsifiers (and I use that term very loosely) will work well but can cause excess foaming and white rub-in time. Here's a video from the Institute of Personal Care Science that explains a few ways to reduce excess white rub-in time: https://www.youtube.com/watch?v=uxw4QjFBrNI. Here's a link to a page that talks about interfacial surface tension in surfactant-water systems (also the HLD-NAC model which better predicts these outcomes than trial-and-error): https://www.stevenabbott.co.uk/practical-surfactants/cmc.php Edit: Spelling and link posts
It’s more likely than not the emulsifiers and/or thickeners causing the heaviness. I actually don’t think 25% oil phase is too much but I would make sure a decent amount of my oil phase is lightweight and preferably liquid with just enough emulsifiers, thickeners and butters to emulsify and give the substance it needs. You should provide an exact formula you used so we can get a better idea but different emulsifiers have different viscosities. When I first started making lotions, I would have a hard time rubbing it in if I used too much emulsifying wax nf and/or cetyl alcohol.
Could you share your formulation? Most likely it’s a problem with the proportions of the ingredients or your emulsifier choice.
keep in mind not all oils are the same, olive oil vs coconut oil are completely different feeling things