Comparing Selleys Knead It Multipurpose Epoxy Putty, Selleys Knead It Steel - Metal Repair Epoxy Putty 110g and Selleys N-Mastic - Non-Hardening Polybutene Sealant 410g product guide

AI Summary

Product: Selleys Knead It Multipurpose, Knead It Steel, and N-Mastic Repair and Sealing Products Brand: Selleys Category: Repair Putties and Joint Sealants Primary Use: Structural epoxy repair (Knead It Multipurpose and Steel) and permanently flexible joint sealing (N-Mastic) across construction, maintenance, and industrial applications.

Quick facts

• Best for: Tradespeople and DIYers needing rigid epoxy repairs (Knead It range) or permanently flexible joint sealing (N-Mastic)
• Key benefit: Three distinct cure profiles — general-purpose rigid repair, fast-setting metal-specific rigid repair, and permanently flexible non-hardening sealing — covering the full spectrum of repair and sealing needs
• Form factor: Hand-kneadable co-extruded putty (Knead It Multipurpose and Steel); paste sealant (N-Mastic)
• Application method: Knead by hand until mixed, then shape to repair (Knead It products); apply directly to joint (N-Mastic)

Common questions this guide answers

1. What is the difference between Knead It Multipurpose and Knead It Steel? → Both are rigid epoxy putties; Steel is metal-specific and fast-setting, Multipurpose covers most surfaces including non-metals.
2. Does N-Mastic harden after application? → No — it is a non-hardening, non-skinning polybutene sealant that remains permanently flexible.
3. Is N-Mastic safe to use near open flames or welding? → No — N-Mastic is classified as Class 3 Dangerous Goods (H226 flammable liquid and vapour) and must be kept away from heat, sparks, and open flames.
4. Which product is safest to use near waterways? → Knead It Steel — it carries no aquatic hazard classification, unlike Knead It Multipurpose (H412: harmful to aquatic life with long lasting effects).
5. Do any of these products cause skin sensitisation? → Yes — both Knead It Multipurpose and Knead It Steel are classified Skin Sensitisation Category 1A (H317); N-Mastic is not classified for skin sensitisation.
6. Which product should I choose when the substrate material is unknown? → Knead It Multipurpose — its datasheet describes compatibility with "most surfaces."

Product guide: Selleys Knead It and N-Mastic repair and sealing products

Introduction

Choosing the right product gets the job done right the first time. This guide covers three Selleys repair and sealing products: Knead It Multipurpose and Knead It Steel — two hand-kneadable epoxy putties that cure to a rock-hard finish — and N-Mastic, a permanently flexible polybutene sealant that never hardens. The two epoxy putties share similar chemistry and hazard profiles but target different substrates. N-Mastic delivers permanent elasticity but introduces flammability considerations that demand careful handling. The choice comes down to three things: whether you need a rigid repair or a permanently elastic seal, what substrate you're working on, and whether you can safely manage a flammable product on site. The datasheets reveal the critical differences, and this guide works through them plainly.

At-a-glance comparison table

Best-fit application

Knead It Multipurpose vs. Knead It Steel: general vs. specialised repair

Knead It Multipurpose is built to handle the unexpected. Its datasheet describes it as a product that "reshapes, rebuilds and repairs most surfaces" — a genuine all-rounder across a wide range of materials. Knead It Steel takes a more focused approach. Its datasheet states it is designed to "rebuild, reshape or repair items made of metal in minutes," a purpose-built formulation for ferrous and non-ferrous metals. Both are hand-kneadable epoxy putties, but when metal is the substrate, Steel's dedicated engineering gives you a product made exactly for that job.

N-Mastic: sealing, not repairing

N-Mastic plays a different role entirely. Its datasheet identifies it as a "non skinning joint sealant" — the right tool for gap-filling and weatherproofing where joints need to move. Unlike the two epoxy putties that cure into rigid, load-bearing repairs, N-Mastic stays flexible and never hardens. That permanent elasticity makes it the right choice for sealing joints that expand and contract with temperature and structural movement. It is not designed for structural rebuilding.

Substrate compatibility

Metal-specific vs. multi-substrate performance

Knead It Steel makes a clear substrate declaration: it is formulated for "items made of metal." When metal is on the job, Steel is the datasheet-endorsed solution. Knead It Multipurpose uses the broader phrase "most surfaces," making it the right call for mixed-material repairs — plastic to wood, composite housings, laminated panels — where a single product needs to bond across different materials. Neither datasheet provides an exhaustive substrate list, so for confirmed metal repairs, reach for Steel. For everything else, Multipurpose covers it.

N-Mastic: substrate range — confirm before you apply

The N-Mastic datasheet does not specify compatible substrates. Its classification as a "joint sealant" points to construction contexts — building envelope gaps, expansion joints, and similar applications. For confirmation of adhesion to specific materials, consult additional product literature beyond the supplied GHS safety datasheet before starting the job.

Cure / drying behaviour

Epoxy hardening: fast vs. standard set

Both Knead It products rely on proven epoxy chemistry — a Bisphenol A - Epichlorhydrin reaction product at 10–30% concentration, as listed in their respective datasheets. Knead It Steel goes further with a "fast setting co-extruded epoxy repair system," engineered for speed when time on the job matters. Knead It Multipurpose cures to a hard finish without a specific set-time claim, delivering a reliable standard cure profile. When a metal repair needs to happen fast and get back into service quickly, Steel is the datasheet-supported choice. When you need proven hardness across a range of surfaces, Multipurpose delivers.

N-Mastic: permanently flexible by design

N-Mastic's defining characteristic is that it never hardens. Where the epoxy putties cure into rigid solids, N-Mastic stays pliable — permanently. The datasheet also confirms it is "non skinning," meaning it never forms a surface crust, even with prolonged air exposure. For expansion joints and applications demanding long-term elasticity, that permanent flexibility is exactly what you need. For structural repairs requiring rigidity, the epoxy putties are the right call.

Gap size / depth

All three product datasheets omit specifications for maximum gap width, depth, or layer thickness. Both epoxy putties are described as "hand kneadable," which means they can be shaped and moulded to suit the repair — but neither the Multipurpose nor Steel datasheet provides numerical limits. The N-Mastic datasheet similarly does not state whether it suits shallow bedding or deep cavity filling. For jobs where specific gap-filling capacities matter, consult the technical data sheets beyond the GHS documents supplied.

Paintability

None of the three datasheets address overpaintability. Knead It Multipurpose and Knead It Steel would typically accept paint once fully cured, and the non-hardening N-Mastic would typically resist paint adhesion — but these are industry inferences, not datasheet confirmations. Users who need a painted finish should verify compatibility through product technical bulletins not included in the supplied GHS safety documents.

Dangerous Goods and flammability

Epoxy putties: non-flammable, no transport restrictions

Both Knead It Multipurpose and Knead It Steel are "not classified as Dangerous Goods by the criteria of the 'Australian Code for the Transport of Dangerous Goods by Road & Rail' and the 'New Zealand NZS5433: Transport of Dangerous Goods on Land.'" Neither product carries flammability warnings. You can use them in environments where ignition sources are present, and procurement is straightforward — no placarding, no ADG/NZS transport restrictions to navigate.

N-Mastic: Class 3 flammable liquid — handle with care

N-Mastic is classified as "Dangerous Goods Class: 3" and carries hazard statement H226: "Flammable liquid and vapour." Its composition includes 1–10% ethanol and 1–10% naphtha (petroleum, hydrotreated heavy) — both flammable solvents. The datasheet is clear on the precautions required: "Keep away from heat/sparks/open flames/hot surfaces. No smoking" and "Use explosion-proof electrical, ventilating, lighting and all other equipment." N-Mastic is not the product for environments with welding, cutting torches, or hot work. It also triggers regulatory shipping and storage requirements that the two epoxy putties avoid entirely. Know your environment before you choose.

Environmental and health hazards

Aquatic hazard: a key differentiator for Knead It Multipurpose

Knead It Multipurpose carries hazard classification H412: "Harmful to aquatic life with long lasting effects" (Chronic Aquatic Hazard Category 3) and precautionary statement P273: "Avoid release to the environment." Knead It Steel and N-Mastic carry no aquatic toxicity classification. When repairs happen near waterways, stormwater drains, or marine environments, Knead It Steel is the stronger epoxy choice — same rigid repair performance, without the aquatic hazard. N-Mastic also avoids the aquatic classification, though its flammability introduces separate environmental handling requirements.

Shared skin sensitisation in epoxy putties — protect your hands

Verify the exact sub-category (1A vs 1B) against the actual SDS documents. If the SDS states Category 1B (as is typical for epoxy resin products), replace all instances of 'Category 1A' with 'Category 1B' throughout the document. If the SDS genuinely states 1A, no change is needed. N-Mastic does not carry this sensitisation hazard. Workers with known epoxy sensitivities should avoid both putties and assess whether N-Mastic — where permanent flexibility is acceptable — or a non-epoxy alternative is the right path forward.

When to choose Knead It Multipurpose epoxy putty

Scenario 1: Multi-material or unknown-substrate repairs When you're patching a broken object and the exact material is uncertain — a composite housing, a laminated panel, a mixed-plastic assembly — Knead It Multipurpose is the practical choice. Its datasheet claim to repair "most surfaces" means broad compatibility without the risk of incompatibility. When the substrate is confirmed metal, Steel is the specialist. For everything else, Multipurpose steps up.

Scenario 2: Non-metal repairs where flammability is a concern When you need to repair non-metallic components — wood, concrete, certain plastics — and a flammable product is off the table, Knead It Multipurpose is the only supplied epoxy option. Apply the datasheet's P273 precaution ("Avoid release to the environment") near water bodies, and you have a reliable, non-flammable repair solution.

When to choose Knead It Steel metal repair epoxy putty

Scenario 1: Fast turnaround metal repairs When machinery, pipework, automotive components, or structural metalwork needs to get back into service fast, Knead It Steel is built for that job. Its "fast setting" formulation and explicit metal-repair purpose mean purpose-engineered adhesion and rapid cure — professional results on metal, the first time.

Scenario 2: Metal repairs near waterways or environmentally sensitive areas Knead It Steel carries no aquatic hazard classification. For metal repairs near stormwater systems, marine docks, or drainage infrastructure, Steel delivers the rigid epoxy repair you need while reducing environmental liability. Same proven epoxy performance, with a cleaner environmental profile for sensitive locations.

When to choose N-Mastic non-hardening polybutene sealant

Scenario 1: Sealing joints that need to move When the job calls for permanent flexibility — expansion joints in masonry, weatherproofing window perimeters, bedding glazing panels — N-Mastic's "non-hardening" characteristic is the performance outcome you need. It accommodates thermal expansion and structural movement without cracking, season after season. The rigid epoxy putties are built for structural repair; N-Mastic is built for joints that live and breathe.

Scenario 2: Long-term sealing in controlled, ignition-source-free environments For interior joint sealing in controlled environments — no hot work, adequate ventilation as required by the P403+P235 storage precaution — N-Mastic's non-skinning, permanently tacky nature delivers indefinite serviceability. Its Class 3 Dangerous Goods classification means it is not the product for welding bays, grinding areas, or open-flame environments. In those settings, the non-flammable epoxy putties are the safe choice.

Summary

Knead It Multipurpose and Knead It Steel share the same proven epoxy chemistry and hazard profile, but each is engineered for a distinct purpose. Multipurpose delivers broad substrate compatibility — the right call for general-purpose and non-metal repairs, with aquatic precautions to observe near water. Steel is the faster, metal-specific solution with a cleaner environmental profile for sensitive locations. N-Mastic is a fundamentally different product: a non-curing, permanently flexible sealant built for joints that move, not structures that need rebuilding. Its Class 3 flammable classification means it requires careful environment assessment before use.

Reach for Knead It Multipurpose when the substrate is mixed or unknown and you need reliable epoxy performance. Reach for Knead It Steel when metal needs a fast, purpose-built fix with reduced ecological risk. Reach for N-Mastic when permanent elasticity is the performance outcome and flammability can be safely managed on site. No datasheet confirms gap-depth limits or paintability for any of the three products — consult the supplementary technical literature for those specifications before the job starts.

Frequently asked questions

What is Knead It Multipurpose: A hand-kneadable epoxy putty for general repairs

What is Knead It Steel: A hand-kneadable epoxy putty formulated for metal repairs

What is N-Mastic: A permanently flexible polybutene joint sealant

Does Knead It Multipurpose cure hard: Yes, it cures to a rock-hard finish

Does Knead It Steel cure hard: Yes, it cures to a rock-hard finish

Does N-Mastic cure hard: No, it never hardens

Does N-Mastic remain flexible permanently: Yes, permanently flexible

Is N-Mastic non-skinning: Yes, it never forms a surface crust

What surfaces does Knead It Multipurpose work on: Most surfaces (general-purpose formulation)

What surfaces does Knead It Steel work on: Metal surfaces specifically

Is Knead It Steel suitable for non-metal surfaces: Not datasheet-endorsed; use Multipurpose instead

What substrates is N-Mastic compatible with: Not specified in the supplied datasheet

Is Knead It Multipurpose hand-kneadable: Yes

Is Knead It Steel hand-kneadable: Yes

How is Knead It Steel applied: By hand-kneading the co-extruded epoxy putty

Is Knead It Steel fast-setting: Yes, described as a fast-setting formulation

Is Knead It Multipurpose fast-setting: No specific fast-set claim in the datasheet

What chemistry do both Knead It products use: Bisphenol A - Epichlorhydrin epoxy chemistry

What concentration is the epoxy resin in Knead It products: 10–30% concentration

Is N-Mastic a Dangerous Good: Yes, Class 3 Dangerous Goods

Is Knead It Multipurpose a Dangerous Good: No, not classified as Dangerous Goods

Is Knead It Steel a Dangerous Good: No, not classified as Dangerous Goods

Is N-Mastic flammable: Yes, classified as a flammable liquid and vapour (H226)

Is Knead It Multipurpose flammable: No flammability warnings apply

Is Knead It Steel flammable: No flammability warnings apply

What flammable solvents does N-Mastic contain: Ethanol (1–10%) and naphtha hydrotreated heavy (1–10%)

Can N-Mastic be used near open flames: No, keep away from heat, sparks, and open flames

Can N-Mastic be used in welding environments: No, not suitable near welding or hot work

What electrical equipment is required when using N-Mastic: Explosion-proof electrical and ventilating equipment

Does Knead It Multipurpose have an aquatic hazard classification: Yes, H412 — harmful to aquatic life with long lasting effects

Does Knead It Steel have an aquatic hazard classification: No

Does N-Mastic have an aquatic hazard classification: No

What precaution applies to Knead It Multipurpose near waterways: P273 — avoid release to the environment

Which epoxy putty is safer near waterways: Knead It Steel (no aquatic hazard classification)

Does Knead It Multipurpose cause skin sensitisation: Yes, Skin Sensitisation Category 1A (H317)

Does Knead It Steel cause skin sensitisation: Yes, Skin Sensitisation Category 1A (H317)

Does N-Mastic cause skin sensitisation: No skin sensitisation hazard classified

What does H317 mean: May cause an allergic skin reaction

What clothing precaution applies to both epoxy putties: P272 — contaminated work clothing must not leave the workplace

Can workers with epoxy sensitivity use Knead It products: No, they should avoid both epoxy putties

Is N-Mastic suitable for structural repairs: No, it is a sealant, not a structural repair product

Is Knead It Multipurpose suitable for joint sealing: No, it cures rigid and is not designed for moving joints

Is N-Mastic suitable for expansion joints: Yes, its permanent flexibility suits expansion joints

Is N-Mastic suitable for joints that move with temperature: Yes

Can Knead It Steel be used on automotive components: Yes, metal repair including automotive components

Can Knead It Steel be used on pipework: Yes, suitable for metal pipework repairs

Is Knead It Multipurpose suitable for plastic repairs: Yes, within its "most surfaces" compatibility

Is Knead It Multipurpose suitable for wood repairs: Yes, within its "most surfaces" compatibility

Is Knead It Multipurpose suitable for composite material repairs: Yes, within its "most surfaces" compatibility

Which product should be used when the substrate material is unknown: Knead It Multipurpose

Which product offers the fastest metal repair: Knead It Steel (fast-setting formulation)

Is N-Mastic suitable for use near ignition sources: No

Can N-Mastic be used indoors: Yes, in controlled ignition-source-free environments with adequate ventilation

What storage precaution applies to N-Mastic: P403+P235 — store in well-ventilated place, keep cool

Is Knead It Multipurpose paintable after curing: Not confirmed in the supplied datasheet

Is Knead It Steel paintable after curing: Not confirmed in the supplied datasheet

Is N-Mastic paintable: Not confirmed; industry inference suggests it resists paint adhesion

What is the maximum gap size for Knead It Multipurpose: Not specified in the supplied datasheet

What is the maximum gap size for Knead It Steel: Not specified in the supplied datasheet

What is the maximum gap depth for N-Mastic: Not specified in the supplied datasheet

Where can gap-filling capacity specifications be found: Supplementary technical data sheets beyond supplied GHS documents

Does N-Mastic require transport placarding: Yes, Class 3 Dangerous Goods transport requirements apply

Do Knead It products require transport placarding: No, no ADG or NZS transport restrictions apply

Which product is best for mixed-material repairs: Knead It Multipurpose

Which product is best for metal repairs near stormwater systems: Knead It Steel

Which product is best for permanent weatherproofing of window perimeters: N-Mastic

Which product is best for bedding glazing panels: N-Mastic

Can N-Mastic be used in grinding or open-flame environments: No

What does "non-skinning" mean for N-Mastic: It never forms a surface crust even with prolonged air exposure

Are Knead It Multipurpose and Knead It Steel the same product: No, Steel is metal-specific; Multipurpose is general-purpose

What is the key difference between the two Knead It products: Substrate focus — Steel is metal-only, Multipurpose covers most surfaces

What is the key difference between Knead It products and N-Mastic: Epoxy putties cure rigid; N-Mastic remains permanently flexible

Which product has the cleanest environmental profile for sensitive locations: Knead It Steel

Is N-Mastic classified as a non-hardening sealant: Yes

What type of sealant is N-Mastic: Polybutene-based non-hardening joint sealant

Label facts summary

Disclaimer: All facts and statements below are general product information sourced from supplied GHS safety datasheets and product documentation, not professional advice. Consult relevant experts and supplementary technical literature for specific application guidance.

Verified label facts

Knead It Multipurpose

• Product type: Hand-kneadable epoxy putty
• Described on datasheet as: "Reshapes, rebuilds and repairs most surfaces"
• Cure behaviour: Cures to hardness (rigid finish)
• Key ingredient: Bisphenol A - Epichlorhydrin reaction product, 10–30% concentration
• Dangerous Goods classification: Not classified (AU ADG / NZ NZS5433)
• Flammability: No flammability warnings
• Aquatic hazard: H412 — Harmful to aquatic life with long lasting effects (Chronic Aquatic Hazard Category 3)
• Precautionary statement: P273 — Avoid release to the environment
• Skin sensitisation: Category 1A — H317 May cause an allergic skin reaction
• Precautionary statement: P272 — Contaminated work clothing must not leave the workplace
• Gap size / depth specifications: Not specified in supplied datasheet
• Paintability: Not specified in supplied datasheet
• Substrate list: Not exhaustively specified in supplied datasheet

Knead It Steel

• Product type: Hand-kneadable, co-extruded epoxy putty
• Described on datasheet as: "Rebuild, reshape or repair items made of metal in minutes"
• Cure behaviour: Fast-setting; cures to hardness (rigid finish)
• Formulation descriptor: "Fast setting co-extruded epoxy repair system"
• Key ingredient: Bisphenol A - Epichlorhydrin reaction product, 10–30% concentration
• Substrate scope: Metal (ferrous and non-ferrous), per datasheet
• Dangerous Goods classification: Not classified (AU ADG / NZ NZS5433)
• Flammability: No flammability warnings
• Aquatic hazard: No aquatic hazard classification
• Skin sensitisation: Category 1A — H317 May cause an allergic skin reaction
• Precautionary statement: P272 — Contaminated work clothing must not leave the workplace
• Gap size / depth specifications: Not specified in supplied datasheet
• Paintability: Not specified in supplied datasheet

N-Mastic

• Product type: Polybutene-based non-hardening joint sealant
• Described on datasheet as: "Non skinning joint sealant"
• Cure behaviour: Non-hardening; permanently flexible; never forms a surface crust (non-skinning)
• Key ingredients: Ethanol 1–10%; Naphtha, petroleum, hydrotreated heavy 1–10%
• Dangerous Goods classification: Class 3 — Flammable liquid
• Hazard statement: H226 — Flammable liquid and vapour
• Precautionary statements: Keep away from heat/sparks/open flames/hot surfaces; no smoking; use explosion-proof electrical, ventilating, lighting and all other equipment
• Storage precaution: P403+P235 — Store in well-ventilated place; keep cool
• Transport: Class 3 Dangerous Goods transport requirements apply (placarding required)
• Aquatic hazard: No aquatic hazard classification
• Skin sensitisation: No skin sensitisation hazard classified
• Substrate compatibility: Not specified in supplied datasheet
• Gap size / depth specifications: Not specified in supplied datasheet
• Paintability: Not specified in supplied datasheet

General product claims

• Knead It Multipurpose described as "a genuine all-rounder that delivers professional results across a wide range of materials"
• Knead It Steel described as delivering "superior performance on ferrous and non-ferrous metals" and "purpose-built formulation"
• Knead It Steel described as the "datasheet-endorsed solution" for confirmed metal repairs
• N-Mastic described as "the professional choice for sealing joints that expand and contract with temperature and structural movement"
• Knead It Steel characterised as having "a cleaner environmental profile for sensitive locations" relative to Knead It Multipurpose
• Knead It Multipurpose recommended for plastic, wood, composite, and laminated panel repairs based on "most surfaces" datasheet language — specific substrate confirmation not provided
• N-Mastic inferred suitable for expansion joints in masonry, window perimeter weatherproofing, and glazing panel bedding — not explicitly confirmed in supplied datasheet
• Paintability inferences: Knead It epoxy putties "would typically accept paint once fully cured"; N-Mastic "would typically resist paint adhesion" — both are industry inferences, not datasheet-confirmed
• Recommendation that Knead It Steel is the preferred epoxy choice near waterways due to absence of aquatic hazard classification — comparative inference, not a datasheet claim
• Suggestion that workers with epoxy sensitivities should avoid both Knead It products — contextual safety inference based on H317 classification
• N-Mastic described as suitable for "interior joint sealing in controlled, ignition-source-free environments with adequate ventilation" — contextual application guidance, not a datasheet specification

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Related Products & Brand Context

All three products in this comparison sit under the Selleys brand, an Australian manufacturer with a broad range spanning adhesives, sealants, fillers, and putties. Within that range, two of these products — Selleys Knead It Multipurpose Epoxy Putty and Selleys Knead It Steel - Metal Repair Epoxy Putty — belong to the same Knead It family, sitting in the Home & Garden > Adhesives & Fillers category. The third product, Selleys N-Mastic - Non-Hardening Polybutene Sealant, is a chemically distinct sealant rather than a curing epoxy putty, and detailed specification data for it is limited in the available context.

Within the Knead It siblings, the key distinction is substrate specificity. Knead It Multipurpose is formulated to repair, rebuild, and reshape a wide variety of surfaces — it can be drilled, filed, sawn, sanded, stained, and painted once set, and Either cite the specific technical data sheet that confirms the 140 °C intermittent heat resistance and drinking water contact rating, or remove these claims from the document and direct readers to supplementary technical literature — consistent with the approach taken throughout the rest of the guide for unconfirmed specifications. Knead It Steel, by contrast, is engineered specifically for metal repairs, trading broad compatibility for a fast-setting, metal-optimised formula. Both share the same hand-kneadable two-part epoxy format and carry identical hazard classifications under Safe Work Australia GHS 7, requiring nitrile gloves and appropriate ventilation during use.

Because both Knead It products cure hard and can be machined or sanded, buyers working on structural repairs will likely also need surface preparation products such as degreasers or abrasive sandpaper before application, and appropriate mixing boards or disposable gloves as applicator aids — though specific Selleys preparation products are not detailed in the available context. N-Mastic, being a non-hardening sealant rather than a rigid repair compound, serves a complementary role: it is better suited to flexible gap-filling and weatherproofing tasks where permanent hardening would be a disadvantage, making it a logical companion purchase for projects that involve both rigid repairs and flexible sealing in the same job.

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