DOWSIL 790 vs DOWSIL 795: which one for the job
Both are Dow silicone building sealants and Cranco carries both. They are built for different joints.
DOWSIL 790 takes more movement than any sealant Cranco carries. DOWSIL 795 covers far more substrates and is the one Dow lists for glazing.
Which to take
Take DOWSIL 790 for stone and masonry that moves. Dow rates it +100/-50% under ASTM C719 and lists joints between natural stone, curtainwall and mullion joints, expansion and control joints, and precast concrete panel joints. Its sheet names sensitive and porous stone facades. It skins in 9 minutes and is tack-free in 31.
Take DOWSIL 795 for glazing and for a mixed run of metal, glass and concrete. Dow lists structural and nonstructural glazing and nine substrates against DOWSIL 790's three.
DOWSIL 790 comes in black and gray only. Neither is paintable, and Dow says the paint film will not stretch with the sealant.
What the data sheets say
| DOWSIL 790 | DOWSIL 795 | |
|---|---|---|
| Chemistry | Silicone | Silicone |
| Movement capability | ASTM C719 extension/compression +100/-50%; ISO 9047 ±25% (highest category) | ±50 percent |
| Skin time | 9 minutes (23°C, 50% R.H.) | 15 minutes |
| Tack-free time | 31 minutes (23°C, 50% R.H.) | 3 hours |
| Cure time | 2.8 mm at 1 day, 5.8 mm at 3 days (23°C, 50% R.H.) | 7 to 14 days curing (25 °C, 50% RH); full adhesion 14 to 21 days |
| Substrates | masonry, concrete, natural stone; sensitive natural stone and porous stone facades | glass, aluminum, steel, painted metal, EIFS, granite and other stone, concrete, brick, plastics |
| Uses | joints between natural stone; curtainwall and mullion joints; expansion and control joints; precast concrete panel joints and other construction joints | structural and nonstructural glazing, panel systems, panel stiffener, weather sealing |
| Paintable | No | No |
| Standards | ISO 11600F 25LM; EN15651 CE MARK; ASTM C920 Type S Grade NS Class 100/50 Use T, NT, M, G, A, O | TT-S 001543A Class A; TT-S-00230C Class A; ASTM C920 Type S Grade NS Class 50 Use NT G A O; ASTM C1184; CAN2-19.13-M82 |
Which DOWSIL sealant takes the most movement?
DOWSIL 790. Dow rates it at +100/-50% extension and compression under ASTM C719, against DOWSIL 795's 50%, and puts it in the highest ISO 9047 category.
What the manufacturers warn about
should not be applied in structural applications, below grade, on brass/copper, to surfaces continuously immersed in water, as interior penetration firestop, in totally confined spaces, or to surfaces that will be painted after application ("The paint film will not stretch with the extension of the sealant and may crack and peel and most likely will not adhere to the sealant.")
DOWSIL™ 795 Silicone Building Sealant should not be used: In structural applications without prior review and approval by your local sales application engineer; In below grade applications; When surface temperatures exceed 50°C (122°F) during installation; On surfaces that are continuously immersed in water; On building materials that bleed oils, plasticizers or solvents that may affect adhesion; On frost laden or wet surfaces; In totally confined joints (the sealant requires atmospheric moisture for cure); If the sealant is intended to be painted (paints do not typically adhere to most silicone sealants); To surfaces in direct contact with food or other food-grade applications
Product pages and related comparisons
- DOWSIL 790 Product details and colours
- DOWSIL 795 Product details and colours
- DOWSIL 791 against DOWSIL 795
- DOWSIL Contractors Weatherproofing Sealant