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Guide

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

By the IDEAL install crew · Frameless glass showers in Massachusetts and New Hampshire since 2014 · Updated

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)
CureAcetic (vinegar smell)Neutral, low odor
Mildew resistantYes—
Safe with brassNo: can turn brass greenYes: non-corrosive to metals
Not forMarble, limestone, mirrors, painted surfacesAquariums, 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.

See how to re-caulk a shower door.

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Products in this guide

CRL 33SMRC Mildew-Resistant Clear Silicone Sealant (10.3 oz Tube)
CRL 33SMRC

Mildew-Resistant Clear Silicone Sealant (10.3 oz Tube)

CRL 33S: clear, mildew-resistant 100% silicone for showers.
$20.48View
CRL RTV408C Neutral-Cure Clear Silicone for Brass Hardware (10.3 oz Tube)
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.
$25.18View
CRL GA1204 Metal Caulking Gun for 10.3 oz Tubes
CRL GA1204

Metal Caulking Gun for 10.3 oz Tubes

Smooth-rod caulking gun for silicone tubes.
$18.38View

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.

More guides

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