Guide
Acetic vs. Neutral-Cure Silicone (33S vs. RTV408) for Showers
Both are 100% silicone. The difference is how they cure, and that matters if your shower has brass hardware.
| CRL 33S (33SMRC) | CRL RTV408 (RTV408C) | |
|---|---|---|
| Cure | Acetic (vinegar smell) | Neutral, low odor |
| Mildew resistant | Yes | — |
| Safe with brass | No: can turn brass green | Yes: non-corrosive to metals |
| Not for | Marble, limestone, mirrors, painted surfaces | Aquariums, acrylic, polyethylene |
Which should you use?
For most showers, mildew-resistant CRL 33SMRC is the go-to. If any of the hardware is brass, use CRL RTV408C: acetic silicone releases acid while it cures, and that acid can turn brass green.
Products in this guide
Common questions
What is the difference between acetic and neutral-cure silicone?
Acetic-cure silicone releases acetic acid (the vinegar smell) while it cures; neutral-cure silicone does not, which makes it safe on metals like brass.
Will 33S silicone damage brass?
It can. Acetic-cure silicone like 33S can turn brass green, so use a neutral-cure silicone like CRL RTV408C with brass hardware.
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