# Acetic vs. Neutral-Cure Silicone (33S vs. RTV408) for Showers | IDEAL Shower Doors

URL: https://idealshowerdoors.com/store/guide/acetic-vs-neutral-cure-silicone-33s-vs-rtv408
Description: Acetic-cure silicone (CRL 33S) vs. neutral-cure silicone (CRL RTV408): which to use around a glass shower door, and why brass hardware needs neutral cure.
Seller: IDEAL Shower Doors, Danvers, MA (https://idealshowerdoors.com/store/)

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Guide

# Acetic vs. Neutral-Cure Silicone (33S vs. RTV408) for Showers

By the [IDEAL install crew](https://idealshowerdoors.com/) · Frameless glass showers in Massachusetts and New Hampshire since 2014 · Updated 10-04-2026

Both are 100% silicone. The difference is how they cure, and that matters if your shower has brass hardware.

|  | [CRL 33S (33SMRC)](https://idealshowerdoors.com/store/p/33smrc) | [CRL RTV408 (RTV408C)](https://idealshowerdoors.com/store/p/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](https://idealshowerdoors.com/store/p/33smrc) is the go-to. If any of the hardware is brass, use [CRL RTV408C](https://idealshowerdoors.com/store/p/rtv408c): acetic silicone releases acid while it cures, and that acid can turn brass green.

See [how to re-caulk a shower door](https://idealshowerdoors.com/store/guide/how-to-recaulk-glass-shower-door).

- [Not sure which seal you need? Use our Seal Finder Pick your door, point to where it leaks and we'll show only the seals that fit your glass. Takes about 30 seconds. Start the Seal Finder →](https://idealshowerdoors.com/store/finder)

## Products in this guide

- [CRL 33SMRC Mildew-Resistant Clear Silicone Sealant (10.3 oz Tube) CRL 33S: clear, mildew-resistant 100% silicone for showers. $20.48 View](https://idealshowerdoors.com/store/p/33smrc)
- [CRL RTV408C Neutral-Cure Clear Silicone for Brass Hardware (10.3 oz Tube) The silicone to use with brass hardware: won't turn brass green. $25.18 View](https://idealshowerdoors.com/store/p/rtv408c)
- [CRL GA1204 Metal Caulking Gun for 10.3 oz Tubes Smooth-rod caulking gun for silicone tubes. $18.38 View](https://idealshowerdoors.com/store/p/ga1204)

## 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](https://idealshowerdoors.com/store/p/rtv408c) 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](https://idealshowerdoors.com/store/p/rtv408c) with brass hardware.

## More guides

[**Sweep vs. drip rail** They do two different jobs at the bottom of the door, and the most popular frameless bottom seals combine both in one piece..](https://idealshowerdoors.com/store/guide/shower-door-sweep-vs-drip-rail)[**H-jamb vs. bulb seal** Both close the gap along the vertical edge of the door.](https://idealshowerdoors.com/store/guide/h-jamb-vs-bulb-seal)[**Clear vs. black seals** Clear and black versions of the same seal fit and work exactly the same.](https://idealshowerdoors.com/store/guide/clear-vs-black-shower-door-seals)[**Shower door leaking at the bottom** Water on the bathroom floor almost always comes from one of four places.](https://idealshowerdoors.com/store/guide/shower-door-leaking-at-bottom)