Polyester and epoxy resins for filling cracks, joints and holes and bonding marble, granite and engineered stone: FS Crack Fill Waterclear, Waterclear Gel Special, Transparent Liquid and Soft, Mastic Liquid and Soft, Flagpox 1005 and 5010, GL 34, plus colouring tints and Epoxy Primer.
Need help choosing? WhatsApp us your stone type and problem or read the stone care buying guide.
Repairing cracks and bonding stone with resins
Cracks, chips and open joints in marble and granite can be filled and bonded so they barely show. Polyester resins (Crack Fill Waterclear, Transparent, Mastic) cure fast, can be tinted to match and polished flush. Epoxy resins (Flagpox, GL 34) give the strongest, most durable bond for structural repairs and reinforcement.
How to fix a crack in marble
- Clean and dry the crack. Remove dust, grease and loose material; resin needs a clean, dry surface to bond.
- Mask the stone around the crack so excess resin is easy to remove.
- Test the filler on a hidden area to check the colour and finish.
- Tint if needed: mix up to 5% FS Colouring Tint into a polyester filler before adding the hardener, and match the colour on a sample.
- Mix exactly: the Flagstone Fix polyester mastics take 1 to 4 g of hardener per 100 g. More than 4% weakens the bond. Epoxies have a fixed A:B ratio on the label; do not change it.
- Fill slightly proud with a spatula, keeping each polyester layer no thicker than 2 mm.
- Let it cure. The polyester mastics can be worked after 6–8 hours; warm weather speeds curing.
- Level and re-polish the repair to match the surrounding finish.
Which resin for which job
| Product | Type | Best for |
|---|---|---|
| FS Crack Fill Waterclear | Polyester, liquid | Filling and fixing natural stone; fine cracks |
| FS Waterclear Gel Special | Polyester, soft gel | Filling and fixing natural stone, vertical work |
| FS Transparent Liquid | Polyester, UV-stable liquid | Surface and joint filling on marble |
| FS Transparent Soft | Polyester, knife-grade gel | Precision filling and bonding |
| FS Mastic Liquid, FS Mastic Soft | Polyester, UV-stable | Joints and bonding natural and engineered stone |
| Flagpox 5010 | Epoxy gel, solvent-free | High-strength bonding of natural and artificial stone |
| Flagpox 1005 | 2-component construction adhesive gel | Strong bonding of various materials |
| GL 34/A + GL 34/B | Epoxy, low viscosity, no fillers | Fixing and repairing natural stone |
| GL 88 | Polyester | Glue for marble and natural stone |
| Epoxy Primer | Water-based primer | Before epoxy, to stop cracks darkening |
| FS Colouring Tint (Epoxy), (Polyester) | Pigment paste | Matching resin colour to the stone |
Coverage and method figures are from the Faber Italy and Flagstone Fix technical data sheets. Always test on a small hidden area first.
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Frequently asked questions
Is epoxy or polyester better for marble crack repair?
Polyester cures fast, can be tinted and polishes well, so it suits most cosmetic cracks and joints. Epoxy gives a stronger, more durable bond for structural repairs and reinforcement.
Can a crack in marble be repaired so it does not show?
Usually it can be made much less visible: tint the filler to match, fill slightly proud, then level and re-polish to the surrounding finish.
How long does marble crack filler take to cure?
The Flagstone Fix polyester mastics can be worked after 6 to 8 hours. Warm weather speeds curing and cold slows it.
How much hardener should I add to polyester mastic?
1 to 4 g per 100 g of mastic. More than 4% weakens the bond.
