Design Essentials STS Express Thermal Therapy Leave-In Sealant – 8 oz
Achieve flawless heat styling with lasting smoothness using Design Essentials STS Express Thermal Therapy Leave-In Sealant. This 8oz treatment is designed to lock in moisture, seal the hair cuticle, and provide long-lasting protection from heat damage — making it the perfect pre-step for blowouts, flat ironing, or silk presses.
Part of the STS Express Smoothing System, this leave-in sealant delivers frizz-free results while maintaining body, bounce, and natural movement. It’s ideal for natural, transitioning, or relaxed hair in need of protection and polish.
Key Benefits:
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Thermal Protection: Guards against heat styling damage from flat irons and blow dryers
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Curl Retention: Helps preserve natural curl pattern and reduces frizz
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Moisture Lock: Seals the hair cuticle to retain hydration and prevent dryness
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Heat Damage Prevention: Forms a protective barrier to reduce long-term damage from styling tools
| Product Size | 8 oz |
|---|---|
| Best For | Natural, transitioning, or relaxed hair |
| Usage | Apply before heat styling (blowouts, flat ironing, silk pressing) |
| Key Ingredients | Hydrolyzed keratin, panthenol, silicones (non-comedogenic) |
FAQ
Can this product be used on color-treated hair?
Yes, this leave-in sealant is safe for color-treated hair and helps protect pigments from heat damage while maintaining vibrancy.
Does it add weight to the hair?
No, it is lightweight and designed to preserve natural movement and body without adding heaviness.
How long does it last before needing reapplication?
It provides up to 4 hours of protection, depending on hair type and styling conditions.

Amy Hill –
Used this before my last flat iron session and noticed less frizz and smoother results. My hair felt softer and didn’t feel dry after styling. Works well with my natural curls and didn’t flatten them like some other products do.
Madeleine Ball –
Great for protecting my relaxed hair from heat. It doesn’t leave a greasy feel and helps maintain bounce. I apply it every time I use a blow dryer or flat iron.
Stephanie Morrison –
My hair has been more resilient since using this sealant. I didn’t see any damage after multiple heat styling sessions. It’s especially helpful when I’m styling my transitioned hair.
Julia Churchill –
Works well as a pre-step. The texture is easy to distribute and dries quickly. I noticed less flyaways and better control during blowouts.
Nathan Wallace –
This is the first product that actually protects my hair without making it feel stiff. I use it every week and my hair stays smooth and healthy after styling.