Epoxy Resins
Two-part epoxies for reinforcing slabs, bonding seams and mitres, fixing sinks and making strong, water-resistant repairs.
- Slab reinforcement
- Seams and mitres
- Undermount sinks
Best to buy: Feb–Apr, Sep–Oct
Read guideSee epoxy vendors
Chemicals buying guideLast updated October 2026
Polyester Mastics
Fast, everyday shop adhesive.
- Price level
- Budget
- Best to buy
- Feb–Apr, Sep–Oct
- Top sources
Photo: USCapitol, Public domain
Overview
What it is
Polyester (knife-grade) mastic is the fast, everyday adhesive of stone shops. Mixed with a small dose of peroxide hardener, it sets in minutes and can be shaped and polished. It's used for filling pits, laminating edges, gluing mosaics and quick repairs.
It comes in solid (for vertical work), semi-fluid and liquid (transparent) grades, and in colours to match stone. It's cheaper and faster than epoxy but weaker, shrinks slightly and isn't ideal for wet or exterior structural bonds.
- Chemistry
- Unsaturated polyester + peroxide hardener (1 to 3%)
- Set time
- About 5 to 15 minutes
- Grades
- Solid, fluid, liquid (transparent)
- Colours
- Straw, white, black, clear and tinted
- Limits
- Shrinkage; lower water and UV resistance
Applications
Best used for
- Filling and repairsMarble and limestone pits and chips.
- Edge laminationsThick-look edges in the shop.
- Quick assemblyFast turnaround jobs.
- Mosaics in dry areasFast-setting bonds.
Think twice for
- Exterior or structural bonds. Use epoxy.
- Long-term wet areas. Moisture weakens polyester bonds.
Origins
Which countries to source from
The producing countries that matter for polyester mastics, what each is known for, and a direct link to vendors there.
Italy Leading source
Stone-specialist mastic makers
- Tenax
- Bellinzoni
Germany
Premium mastics
- Akemi
Turkey
Regional supply
- Local makers
China
Value mastics
- Broad range of makers
Timing
Best time of year to buy
Chemicals are made to order all year. Ship resins and water-based products in mild months: summer heat shortens shelf life in transit, and winter cold can freeze or crystallise them.
- Jan: slower or pricier
- Feb: best time to buy
- Mar: best time to buy
- Apr: best time to buy
- May: normal
- Jun: normal
- Jul: slower or pricier
- Aug: slower or pricier
- Sep: best time to buy
- Oct: best time to buy
- Nov: normal
- Dec: slower or pricier
Best time to buy Normal Slower or pricier
- Epoxy hardeners and water-based sealers can crystallise or freeze in unheated containers in winter.
- Summer container temperatures can exceed 50 °C, which shortens the shelf life of polyesters and catalysts.
- Most products have a 12 to 24 month shelf life: buy for your usage, not for a discount.
Import costs
Tariffs and import duties
Base duties for the main import markets, the extra US surcharge by origin, and the trade remedies to check before you quote a landed price.
HS codes
- 3506.91Prepared adhesives based on polymers
- 3214.10Mastics and resin cements
Base import duty (MFN)
United States2.1% to 3.7%
European Union5% to 6.5%
United Kingdom4% to 6%
Importing into the US? Add the 2026 origin surcharge
Section 301 rates in force since 24 July 2026, stacked on the MFN rate above.
- Italy10% min.Section 301 (2026) tops the duty up to at least 10% in total; no surcharge if MFN is already higher.
- Germany10% min.Section 301 (2026) tops the duty up to at least 10% in total; no surcharge if MFN is already higher.
- Turkey+12.5%Section 301 (2026) adds 12.5% on top of the MFN rate.
- China+12.5% & 30112.5% Section 301 (2026) plus the legacy China Section 301 duty (25% on most stone and machinery lines), on top of MFN.
- Many resins, solvents and sealers are dangerous goods: they need an SDS and correct IMDG packing and labels for sea freight.
- EU importers take on REACH registration duties for chemicals above 1 tonne a year; US importers must certify TSCA compliance.
Rates checked October 2026. Indicative rates for planning, not a customs ruling. Duties depend on the exact tariff line, origin, trade agreements and the rules in force on the day of entry. Confirm with a licensed customs broker before you price an order.
Before you order
Buying checklist
- 1Match colour and consistency to the job.
- 2Keep hardener at 1 to 3%: too much burns and discolours stone.
- 3Ventilate: styrene odour and VOCs.
- 4Don't use on wet or humid stone.
- 5Check shelf life, usually about 12 months.
Price level: Inexpensive and used in volume.
Vendor Network
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Keep reading
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- Floor and wall tiles
- Large-format stone and sintered slabs
- Wet rooms and pools
Best to buy: Feb–Apr, Sep–Oct
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- Kitchen worktops
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- Façades
Best to buy: Feb–Apr, Sep–Oct
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