The short answer: for natural stone you need a silicone developed specifically for it – not a standard sanitary silicone. Ordinary silicone can cause permanent edge-zone staining (greasy rings) on porous stone. Proven professional products: OTTOSEAL S70 (premium, the widest colour range) and OTTOSEAL S117 (budget-conscious, standard colours).
The quick decision: S70 or S117?
OTTOSEAL S70 Premium
- Over 35 shades, including "textured" colours with a stone-like surface and matt shades
- Guaranteed free of edge-zone staining – tested to ISO 16938-1 (SKZ Würzburg) and ASTM C 1248 (DL Laboratories New York)
- The widest field of use: natural stone swimming pools including underwater joints as well as painted and enamelled glass
- TOXPROOF-certified (TÜV Rheinland), suitable per IVD guidance note no. 9
OTTOSEAL S117 Value pick
- 11 standard colours for the most common natural stone tones
- Guaranteed free of edge-zone staining – tested to EN 15651 part 1 (F EXT-INT CC 20LM) and part 3 (XS1)
- For jointing, movement joints and movement-accommodating bonding of natural stone to metal
- French VOC emission class A+, certified to GOS
Why is ordinary sanitary silicone not enough?
Joints on natural stone such as marble, granite, sandstone or quartzite are often porous and absorbent. Conventional silicones can migrate into them and leave permanent, oil-like rings around the joint – what is known as edge-zone staining. Once it has happened, that damage usually cannot be removed without trace. Natural stone silicones such as OTTOSEAL S70 and OTTOSEAL S117 are formulated specifically to prevent exactly that and have been tested accordingly to recognised test methods. You will find the full range in the category natural stone silicone. If stains have already appeared, our guide Stains on natural stone from the wrong silicone shows how to proceed.
The comparison in detail
| Criterion | OTTOSEAL S70 (Premium) | OTTOSEAL S117 |
|---|---|---|
| Colour range | Over 35 shades, including "textured" and matt shades | 11 standard colours (including anthracite, bahama beige, concrete grey, manhattan, white) |
| Edge-zone protection tested to | ISO 16938-1 (SKZ Würzburg), ASTM C 1248 (DL Laboratories New York) | EN 15651 part 1 (F EXT-INT CC 20LM), part 3 (XS1) |
| Further certificates | TOXPROOF (TÜV Rheinland), IVD guidance note no. 9 | French VOC class A+, GOS-certified, IVD guidance note no. 3-1+3-2+14+23+25+27 |
| Field of use | Marble & all natural stones, movement joints, bonding to metal, natural stone swimming pools including underwater joints, painted and enamelled glass, mirror sealing | Marble & all natural stones, movement joints in walls and facades, movement-accommodating bonding of natural stone to metal |
| Application temperature | +5 °C to +35 °C | +5 °C to +35 °C |
| Temperature-resistant | -40 °C to +180 °C | -40 °C to +180 °C |
| Skin-forming time | approx. 5 min (+23 °C, 50 % rel. humidity) | approx. 5 min (+23 °C, 50 % rel. humidity) |
| Price | Premium segment | Budget-conscious entry |
Do I need a primer?
With both products the bonding faces must be clean, free of grease, dry and sound – clean non-porous substrates with OTTO Cleaner T, and free porous substrates of loose particles mechanically (with a wire brush, for instance). On many natural stones such as granite, Jura, Bianco Sardo or Kashmir White, OTTOSEAL S70 achieves good adhesion without a primer according to the manufacturer. On some heavily polished or sensitive stones such as Carrara White, Statuario, Calcatta or Rosso Verona the manufacturer recommends a primer beforehand. A bonding agent suitable for natural stone can be found in the Otto Primer 1102 natural stone & sandstone primer, for example. When in doubt the rule is: always make a trial application on an inconspicuous spot first.
How much silicone you need for your joint depends on joint width and depth – our Ottoseal silicone usage table provides guide figures.
An alternative for particularly sensitive stones: OTTOSEAL S80
For natural stones where the lowest possible odour is called for, OTTO Chemie offers another low-odour natural stone silicone in OTTOSEAL S80, which likewise causes no edge-zone discolouration and adheres to many natural stones without a primer.
Common questions about silicone for natural stone
Which silicone is best suited to natural stone?
A silicone developed specifically for natural stone such as OTTOSEAL S70 or OTTOSEAL S117. Both demonstrably prevent edge-zone staining; the S70 offers the wider colour range including textured and matt shades, the S117 is the cheaper alternative with standard colours.
Why must I not use ordinary sanitary silicone on natural stone?
Conventional silicones can migrate into porous natural stone and cause permanent, oil-like edge stains (edge-zone staining). Natural stone silicones such as OTTOSEAL S70 and S117 are formulated specifically to prevent exactly that and are tested accordingly.
What is the difference between OTTOSEAL S70 and S117?
Both prevent edge-zone staining on natural stone. The S70 offers over 35 shades including textured and matt finishes as well as a wider field of use extending to natural stone swimming pools and painted glass, and is tested to ISO 16938-1 and ASTM C 1248. The S117 comes with 11 standard colours, is tested to EN 15651 and is the more economical choice for standard joints.
Do I need a primer for natural stone?
On most natural stones such as granite, Jura or Bianco Sardo, OTTOSEAL S70 achieves good adhesion without a primer according to the manufacturer. On heavily polished or sensitive stones such as Carrara White or Statuario the manufacturer recommends a primer beforehand, for example the Otto Primer 1102 natural stone & sandstone primer.
How much natural stone silicone do I need for my joint?
Usage depends on joint width and depth. You will find an overview with guide figures in our Ottoseal silicone usage table.
What do I do if stains from the wrong silicone have already appeared?
Once edge-zone staining has occurred it usually cannot be removed without trace. Our guide Stains on natural stone from the wrong silicone explains how to proceed and which products help.
