Brass to Sandstone Adhesive
What glue can I use to fix brass house numbers to a genuine sandstone letterbox?
Check the Liquid Nails Landscape specification
Selleys' product page and its dated technical sheet disagree on Landscape's chemistry, colour, paintability and pack size. Landscape figures below from the November 2020 technical sheet describe that document, not a confirmed specification for every current cartridge. Confirm the matching instructions before painting, choosing a colour, or relying on cure and loading times. See the source comparison and dated documents.
Selleys nominates three products for this job, and the right one depends on whether the adhesive will be visible.
- Selleys Hold Up — white.
- Selleys Liquid Nails Landscape — grey. For Landscape, confirm the specification for your cartridge: the manufacturer sources disagree.
- Liquid Nails Mirror & Metal — if you would prefer a clear or translucent adhesive.
Whichever you choose, the numbers will need to be held in place with tape until the adhesive has cured sufficiently — including with Hold Up, despite the name. Full cure is 2 to 3 days.
Which of the three to pick
| Property | Hold Up | Liquid Nails Landscape | Mirror & Metal |
|---|---|---|---|
| Technology | Sil-X | Neutral cure silicone | Neutral cure silicone |
| Colour | White / off-white | Grey | Translucent |
| Skin time | Approx. 45 min | 10–15 minutes | 10–15 minutes (weather dependent) |
| Tack free time | — | 35 ± 5 minutes | 45 minutes |
| Cure | At least 48 hours | 2 mm / 24 hrs | 2 mm / day |
| Support until | At least 48 hours, undisturbed | At least 24 hours before loading | Normally 72 hours |
| Holds | 240 kg/m² (tube) or 360 kg/m² (cartridge) on vertical surfaces | — | — |
| Packaging | 130 g tube; 290 mL cartridge | 300 g cartridge | 310 g cartridge |
Indicative data only, not intended for the preparation of specifications.
Go translucent if the adhesive might show. House numbers usually have a small footprint and stand slightly proud, so a white or grey adhesive squeezing out around the edge of a numeral is visible from the street. Mirror & Metal is translucent and is specifically listed for metals including brass, and for house numbers on exterior walls. It also carries the widest temperature range of the three at −60°C to 150°C with high UV resistance, suitable for inside and outside the home, and it is non-corrosive — which matters where brass is involved.
Go grey with Landscape if the sandstone is grey-toned and the numbers are chunky. Landscape is intended for stone and masonry, is highly weather resistant and shock proof, and its grey disappears against most stone. For Landscape, confirm the specification for your cartridge: the manufacturer sources disagree.
Go white with Hold Up for small, light numerals on a pale sandstone. Hold Up is the easiest to work with: it is adjustable for up to 15 minutes, which is useful when you are lining up six numerals by eye.
What sandstone does to the job
Genuine sandstone is porous, and often soft and slightly friable at the surface. Two consequences follow.
Brush the surface clean and check it is sound. Liquid Nails Landscape states it is not for soft or crumbly materials, and a weathered sandstone face can be exactly that. If a fingernail brings sand off the surface, the adhesive will hold the sand and the sand will not hold the stone. Brush back to a sound face first.
The porosity is on your side for curing. All three products cure with atmospheric moisture, and porous stone gives them access to it. Brass, by contrast, is entirely non-porous, so the cure works inwards from the perimeter of each numeral. This is why a thin, well-spread bed cures far faster than a thick blob, and why the 2 to 3 day figure is realistic rather than cautious.
How to fix the numbers
- Make sure the sandstone is sound, dry and free from oil, grease, dust and loose powdery material. Brush off any friable surface. If needed, clean with mineral turpentine and allow it to dry.
- Clean the back of each brass numeral. New brass often carries a lacquer or an oily film from handling — degrease it.
- Mark your positions on the stone first, with a pencil line and a level. Once the adhesive is on, you have minutes, not hours.
- Cut the cartridge tip, fit the nozzle and cut it to a suitable size opening (approximately 5 mm). Use a good-quality caulking gun.
- Apply the adhesive to the back of each numeral in beads or dobs, kept in from the edges to minimise squeeze-out — at least 12 mm in from the edges with Landscape. For Landscape, confirm the specification for your cartridge: the manufacturer sources disagree.
- Press each numeral onto the stone before the product skins — within 5 minutes for Landscape and Mirror & Metal — with enough pressure to spread the adhesive between both surfaces. For Landscape, confirm the specification for your cartridge: the manufacturer sources disagree.
- Tape each numeral in place. Masking tape across the face and onto the stone above and below is enough.
- Do not wipe squeeze-out. Wait until the product cures, then trim it with a sharp blade, avoiding cutting into the bond. Spilt or smeared adhesive is best left to cure and then removed by abrasion.
- Leave the tape on for the full cure period — 2 to 3 days.
Limitations
- Hold Up: not for some plastics (PE, PP, PTFE) or some rubbers; water resistant but not suitable for permanent water immersion; must not be disturbed until cured, at least 48 hours. For heavy objects, overhead applications and non-porous materials such as glass and metals, additional supports are recommended during cure — brass numerals on a vertical face are that case, which is why the taping instruction applies.
- Liquid Nails Landscape: not for soft or crumbly materials; do not use as the sole bonding agent for structural bonding; if repositioning, fresh adhesive must be applied.
- Mirror & Metal: freshly painted surfaces should be allowed to dry for at least 7 days before the job, and compatibility on painted surfaces should be tested first. Glue lines may be visible through surfaces that are not perfectly opaque.
Clean up
Uncured product removes with mineral turpentine (Landscape and Mirror & Metal) or white spirits or turps (Hold Up), immediately, before the product cures. Cured product comes off with Selleys Sealant Remover or by mechanical action — and on soft sandstone, mechanical action will mark the stone, so clean up while it is wet.
Common questions about fixing brass to sandstone
How long do I tape the numbers for?
Full cure is 2 to 3 days. Hold Up must not be disturbed for at least 48 hours; Mirror & Metal normally needs support for 72 hours.
Do I really need tape with Hold Up?
Yes. Selleys says the numbers will need to be held in place with tape until the adhesive has cured sufficiently, even with Hold Up, and the data sheet recommends additional supports for non-porous materials such as metals.
Which one will not show?
Liquid Nails Mirror & Metal, which is translucent. Hold Up is white and Landscape is grey. For Landscape, confirm the specification for your cartridge: the manufacturer sources disagree.
Will it corrode the brass?
Landscape and Mirror & Metal are both neutral cure silicones, and Mirror & Metal is stated to be non-corrosive. Brass is among the metals it is listed for. For Landscape, confirm the specification for your cartridge: the manufacturer sources disagree.
Will it survive weather?
Landscape offers superior weather resistance. Mirror & Metal has high temperature resistance from −60°C to 150°C and high UV resistance, suitable for outside the home.
My sandstone surface is crumbly. What now?
Brush back to a sound face before you start. Landscape states it is not for soft or crumbly materials.
Can I reposition a numeral after it touches down?
Hold Up is adjustable for up to 15 minutes. With Landscape, if you reposition, fresh adhesive must be applied to achieve bonding.
How much do I need?
A 130 g tube of Hold Up is ample for a set of house numbers. The cartridges are 290 mL to 310 g and are sized for much larger jobs.
How do I clean up the squeeze-out?
Do not wipe it. Let it cure and trim it with a sharp blade, or remove smears by abrasion once cured.
What adhesive question does this Selleys page address?
The page addresses the question of what glue can be used to attach brass house numbers to a genuine sandstone letterbox.
What adhesive is recommended for bonding brass house numbers to a sandstone letterbox?
Selleys® Liquid Nails® Flex is recommended, as it is compatible with both brass (a compatible metal material) and sandstone (a non-porous substrate material).
Why is Liquid Nails Flex suitable for bonding brass to sandstone?
Liquid Nails Flex is strong, flexible, and has high bond strength with up to 400% stretch capability, adheres to all building materials including both porous and non-porous surfaces, bridges gaps up to 9mm, forms a water-resistant seal once cured, and is suitable for both interior and exterior applications.
What is the service temperature range for Liquid Nails Flex?
Liquid Nails Flex has a service temperature range of -20°C to +70°C.
Can Liquid Nails Flex be used outdoors on a sandstone letterbox?
Yes, Liquid Nails Flex forms a water-resistant seal once cured, making it suitable for both interior and exterior applications like an outdoor sandstone letterbox.
How should surfaces be prepared before applying Liquid Nails Flex to bond brass and sandstone?
Surfaces should be clean, sound, and free of dust, oil, rust, and other contaminants. The non-porous brass surface should be cleaned with a clean cloth dampened with IPA or white spirit, wiping in one direction only, and immediately followed by wiping with a clean, dry cloth.
Does Liquid Nails Flex have any curing or environmental characteristics worth noting?
Yes, Liquid Nails Flex is fast curing and has low VOC (volatile organic compound) content.
What gap size can Liquid Nails Flex accommodate when bonding surfaces like brass and sandstone?
Liquid Nails Flex can bridge gaps up to 9mm, which helps accommodate any surface irregularities between the brass and sandstone.