Newton Newtonite 801 Mastic Sealant

Health & Safety Recommendations

Before using Newton Newtonite 801 Mastic, read the product label and safety data sheet, and follow normal site hygiene procedures. Wear suitable gloves when handling the product, especially when applying it repeatedly around damp proof membrane fixing plugs or service penetrations. Eye protection is recommended when cutting the nozzle, applying the mastic overhead, working around drilled holes or sealing awkward recesses. Avoid unnecessary contact with skin and eyes, and wash hands thoroughly after use.

Newtonite 801 Mastic should only be used in well-ventilated rooms, with good airflow maintained throughout application and curing. This is especially important in enclosed internal areas such as basements, cellars, cupboards, service zones and refurbishment spaces where air movement may be limited. Although Newtonite 801 Mastic is a non-toxic, solvent-free silicone mastic, ventilation should still be treated as part of good working practice. Do not eat, drink or smoke while using the product, and keep the working area clean to prevent uncured mastic being transferred onto finished surfaces.

Surface Preparation

All surfaces should be dry, clean and free from dust, grease, oil, loose material and other contaminants before Newtonite 801 Mastic is applied. The effectiveness of the seal depends on the mastic making close contact with the plug head, membrane surface, substrate, joint edge or penetration detail. If the surface is dusty, greasy or contaminated, adhesion may be reduced and the finished seal may not perform as intended.

Where necessary, degrease the surface with MEK, alcohol or ethanol before application, and allow cleaned areas to dry fully before applying the mastic. When using Newtonite 801 Mastic around damp proof membrane fixing plugs, ensure the membrane face around the fixing position is clean and that drilling dust has been removed from the pilot hole area. Loose dust or debris trapped around the fixing head can interrupt the gasket effect and reduce the quality of the damp proof seal.

For general construction sealing, preliminary adhesion and compatibility tests are recommended before full application. This is particularly important on unusual materials, coated surfaces, aged substrates, plastics, polished surfaces, painted backgrounds or any material where previous treatments may affect adhesion. The product is suitable for many building and engineering materials, but testing helps confirm the sealant will perform correctly on the exact substrate being used.

Application Method

Cut the supplied cartridge nozzle to the required bead size and load the cartridge into a suitable cartridge gun. The nozzle should be cut to deliver enough Newtonite 801 Mastic to fill the required sealing area properly. Avoid cutting the nozzle too small if the mastic needs to fill a deeper recess, service penetration or plug head detail, as a thin bead may not provide a complete seal.

When using Newtonite 801 Mastic as a damp proof membrane fixing plug sealant, drill the pilot holes through the membrane and into the substrate in preparation for the fixing plugs. Before inserting the plug, apply the mastic in a continuous ring either around the inside face of the fixing head or around the pilot hole. When the fixing plug is inserted and driven home, the mastic should compress between the plug head and the membrane to form a damp proof gasket. This helps seal the penetration and reduces the risk of moisture, salts or staining bridging from the damp wall through to the new internal surface.

When sealing service penetrations, protrusions, cable routes, pipe entries, recesses or small joint details, apply Newtonite 801 Mastic directly into the opening using the cartridge gun. The recess, joint or penetration should be filled sufficiently to create a complete seal around the detail. Pay close attention to irregular shapes, gaps around pipework, corners, plug heads and uneven membrane surfaces. The product should not be applied as a very thin smear where a proper seal is required, as thin layers may not provide enough material to accommodate movement or maintain a reliable barrier.

Where a neater finish is required, use a stopping knife to smooth the surface of the mastic before skin formation begins. Tooling should be carried out carefully so the mastic remains in full contact with the plug head, membrane, joint edge or penetration. Avoid dragging the product away from the area being sealed. If the mastic is being used behind a fixing plug, the plug should be inserted while the mastic is still uncured so that the material can compress and form the intended gasket.

Curing Time

Newtonite 801 Mastic has a skin forming time of approximately 25 minutes at 23°C and 50% relative humidity. This provides a practical working period for applying the mastic around membrane fixing plugs, smoothing visible details and sealing service penetrations. Skin formation may be faster in warmer or drier conditions, and slower in colder or more humid environments.

The vulcanisation rate is approximately 2.5 to 3mm every 24 hours at 23°C and 50% relative humidity. Full cure time will depend on bead thickness, depth of the recess, temperature, humidity, ventilation and the amount of sealant applied. Deep sections and enclosed details will take longer to cure than shallow exposed beads. The application temperature should be between +5°C and +40°C. Once cured, Newtonite 801 Mastic provides temperature resistance from -50°C to +150°C.

When used around damp proof membrane plug fixings, the plug can normally be fitted immediately after the mastic is applied, allowing the uncured material to compress and form the gasket. Avoid disturbing the sealed fixing unnecessarily while the mastic cures. Where the mastic has been used in larger service penetrations or deeper recesses, allow enough curing time before covering, stressing, decorating or exposing the area to movement.

Cleaning

Uncured Newtonite 801 Mastic should be removed from tools, hands and adjacent surfaces as soon as possible using Soudal Swipex Wipes. Cleaning should be carried out while the sealant is still fresh, as silicone mastic becomes much harder to remove once curing has started. Take particular care around visible membrane faces, finished walls, plug heads, pipework and surrounding surfaces where excess product may be noticeable.

Once cured, unwanted Newtonite 801 Mastic can only be removed mechanically, with the aid of Soudal Sealant Remover Spray where suitable. Mechanical removal may involve careful cutting, scraping or trimming, depending on the surface. Care should be taken not to damage damp proof membranes, surrounding finishes, plug heads, pipework or adjacent substrates during removal. Good application control throughout is strongly recommended, as preventing excess smears is far easier than removing cured material afterwards.

Limitations

Newtonite 801 Mastic should not be applied to wet, greasy, dusty or unstable surfaces. All surfaces should be dry and properly prepared before application. It should not be used in situations where the mastic cannot make proper contact with the surface, or where the sealant is applied so thinly that it cannot form an effective gasket or seal.

The product should not be treated as a replacement for correct damp proof membrane installation. It is used to seal fixing penetrations, plug heads, service entries, recesses and detailing points, but the membrane system itself must still be correctly specified, fixed and detailed. Fixing density, plug type, membrane type and substrate condition should all be checked before installation begins.

Preliminary tests are recommended before general use, particularly on sensitive, coated, unusual or difficult substrates. Do not assume compatibility on every plastic, paint, coating or treated surface without testing first. Application should be carried out between +5°C and +40°C, and the product should only be used in areas with suitable ventilation during both application and cure.

Other Information

Newton Newtonite 801 Mastic is a single-component silicone mastic used as a damp proof membrane sealant, membrane fixing plug sealant and multipurpose construction sealant. It is particularly useful for sealing plaster plug fixings in damp proof membrane systems, helping prevent moisture bridges, efflorescent salts and staining from reaching the new internal finish. It can also be used around service penetrations and protrusions through the membrane or substrate where a flexible seal is required.

At 23°C and 50% relative humidity, Newtonite 801 Mastic has a skin forming time of approximately 25 minutes and a vulcanisation rate of 2.5 to 3mm every 24 hours. It has a density of 1.36 g/ml under ISO 1183 and a cured hardness of Shore A 20 under ISO 868, giving a soft, flexible seal well suited to movement and detailing work. Its elastic recovery is greater than 90% under ISO 7389, with a deformation capability of 25%, a modulus at 100% elongation of 0.32 N/mm² under ISO 8339 and an elongation at break of 350%.

The VOC content is less than 100 g/l, and the cured mastic has temperature resistance from -50°C to +150°C. These figures support its use in demanding damp proofing, refurbishment and building sealing applications where flexibility, adhesion and long-term durability all matter. For the best results, apply Newtonite 801 Mastic carefully, use enough material to form a complete seal, and ensure plug heads, penetrations and membrane details are properly compressed or tooled before the product skins.

Q) What is Newton Newtonite 801 Mastic used for?

A) Newton Newtonite 801 Mastic is used as a flexible sealing mastic for damp proof membrane systems, particularly around fixing plugs, plug heads, service entries and detailing points. Its main role is to help stop moisture, efflorescent salts and damp staining from tracking through membrane penetrations and affecting the new internal finish. When a damp proof membrane is fixed to a wall, each drilled plug hole can create a potential bridge between the damp substrate and the plaster, render or plasterboard surface. Newtonite 801 Mastic is applied before the plug is fitted, creating a damp proof gasket that helps maintain separation between the contaminated wall and the finished room.

Q) How does Newton Newtonite 801 Mastic help prevent moisture bridging?

A) Newton Newtonite 801 Mastic helps prevent moisture bridging by sealing the vulnerable fixing point before the membrane plug is fully installed. In a membrane system, the membrane separates the new internal finish from damp, stained or salt-contaminated masonry. However, a mechanical fixing passes through that membrane and into the wall, so the fixing hole must be detailed correctly. By applying Newtonite 801 Mastic around the pilot hole or fixing head, the mastic compresses as the plug is driven home and forms a flexible gasket. This helps block moisture and salts from travelling through the plug hole and spoiling the plaster, render or board finish.

Q) Where should Newtonite 801 Mastic be used in a damp proof membrane system?

A) Newtonite 801 Mastic is most commonly used around damp proof membrane fixing plugs, especially where the wall behind the membrane is damp, stained or salt contaminated. It is suitable for sealing plug heads, pilot holes, protrusions, service penetrations, pipes, cable routes and small detailing gaps where the membrane or substrate has been interrupted. It is particularly useful in internal damp wall refurbishment where meshed membranes are being fixed before plaster, render or plasterboard finishes are applied. The product should be used wherever a flexible, durable, damp proof seal is needed around a fixing or detail, but it should always form part of a correctly designed membrane installation.

Q) Which membrane fixing plugs can Newton Newtonite 801 Mastic be used with?

A) Newton Newtonite 801 Mastic can be used with a range of damp proof membrane fixing plugs where a sealed fixing detail is required. The information provided specifically includes Newton Newtonite Mesh Plugs, Platinum Mesh Fix Plugs, Platon Plaster Plugs, Wykamol CM Plaster Membrane Plugs Without Seals and Platinum Cob Plugs. In each case, the mastic is normally applied around the plug head or pilot hole before the plug is installed, so it compresses between the plug and membrane. This creates a damp proof gasket and helps reduce the risk of moisture, salts or staining moving through the fixing penetration into the new internal wall finish.

Q) Is Newtonite 801 Mastic suitable for sealing service penetrations?

A) Yes, Newtonite 801 Mastic is well suited to sealing service penetrations through damp proof membrane systems, including pipes, cables, conduits and similar entries. Service penetrations are often weak points because they interrupt the membrane layer and can create routes for moisture or damp air movement if they are not properly sealed. Newtonite 801 Mastic can be applied around the service entry to fill the gap and create a flexible seal that accommodates small movement and vibration. For best results, the area should be clean, dry and free from loose dust before application, and enough mastic should be used to fully seal the penetration rather than simply smearing the surface.

Q) What surfaces does Newton Newtonite 801 Mastic bond to?

A) Newton Newtonite 801 Mastic has strong adhesion to many common construction and engineering materials, often without primer. Suitable substrates listed include laminated glass, double glass, aluminium, steel, stainless steel, anodised steel, treated wood, PVC, concrete and brick. Its compatibility with alkaline materials such as concrete and masonry makes it especially useful for remedial damp proofing and refurbishment work, where sealants frequently need to bond to mineral substrates. Even so, good surface preparation is still essential. The surface should be dry, clean and free from dust, grease, oil and loose material, and preliminary adhesion tests are recommended on unusual, coated, aged or sensitive surfaces.

Q) How should surfaces be prepared before applying Newtonite 801 Mastic?

A) Surfaces should be dry, clean and stable before Newtonite 801 Mastic is applied. Dust, grease, oil, drilling debris, loose material and other contaminants should be removed because they can prevent the mastic from bonding properly. When sealing membrane fixing plugs, the membrane face around the pilot hole should be wiped clean and drilling dust should be cleared from the fixing area before the plug is fitted. Where necessary, surfaces can be degreased with MEK, alcohol or ethanol, then allowed to dry fully before application. On unusual substrates, coated materials, plastics, polished surfaces or previously treated backgrounds, a small adhesion and compatibility test should be carried out first.

Q) How do you apply Newton Newtonite 801 Mastic around plaster plugs?

A) To apply Newton Newtonite 801 Mastic around plaster plugs, first drill the fixing hole through the membrane and into the substrate as required by the membrane system. Before inserting the plug, apply a continuous ring of mastic around the inside face of the plug head or around the pilot hole. The plug should then be inserted while the mastic is still uncured and driven home so the mastic compresses between the plug head and the membrane surface. This forms the damp proof gasket. The aim is to create complete contact around the fixing point, so avoid using too little material or leaving gaps in the mastic ring.

Q) Can Newtonite 801 Mastic help stop salt staining on new plaster?

A) Newtonite 801 Mastic can help reduce the risk of salt staining where staining could otherwise track through membrane fixing points. In damp or salt-contaminated walls, efflorescent salts can migrate through moisture pathways and spoil new plaster, render or board finishes. A damp proof membrane helps isolate the finish from the wall, but the fixing holes still need proper detailing. By sealing the plug head and penetration, Newtonite 801 Mastic helps prevent salts and damp staining from bridging through the fixing. It will not remove salts from the wall or replace correct membrane specification, but it is a valuable detailing product for protecting the finished surface.

Q) How long does Newton Newtonite 801 Mastic take to cure?

A) Newton Newtonite 801 Mastic has a skin forming time of approximately 25 minutes at 23°C and 50% relative humidity. Its vulcanisation rate is approximately 2.5mm to 3mm every 24 hours under the same conditions. Actual curing time depends on bead depth, sealant thickness, temperature, humidity, ventilation and how enclosed the detail is. A thin exposed bead will cure more quickly than a deep service penetration or recess. When used around membrane fixing plugs, the plug can normally be fitted immediately after application so the uncured mastic compresses into a gasket. Larger sealed details should be allowed enough curing time before being covered, stressed or decorated.

Q) What are the main technical benefits of Newtonite 801 Mastic?

A) Newtonite 801 Mastic offers a strong combination of flexibility, adhesion and durability. It has a density of 1.36g/ml under ISO 1183 and cures to a Shore A hardness of 20 under ISO 868, giving a soft, flexible seal. Elastic recovery is greater than 90% under ISO 7389, with a deformation capability of 25%, a modulus at 100% elongation of 0.32N/mm² and elongation at break of 350% under ISO 8339. These values show that the cured mastic can stretch, recover and maintain contact around fixings and detailing points. It also has temperature resistance from -50°C to +150°C and VOC content below 100g/l.

Q) Is Newton Newtonite 801 Mastic solvent-free and suitable for internal work?

A) Yes, Newton Newtonite 801 Mastic is described as non-toxic, solvent-free and single component, which makes it practical for internal damp proofing, refurbishment and membrane detailing work. It is ready to use from the cartridge and does not need mixing, which helps keep application straightforward on site. Although the product is solvent-free, good ventilation should still be maintained during application and curing, especially in confined internal spaces such as cellars, basements, cupboards and service zones. Suitable gloves should be worn, eye protection is recommended, and normal site hygiene should be followed. The product should be kept away from children and handled in line with the label and safety data sheet.

Q) How do you clean Newtonite 801 Mastic after application?

A) Uncured Newtonite 801 Mastic should be cleaned immediately using Soudal Swipex Wipes. Prompt cleaning is important because silicone mastic becomes much harder to remove once curing has started. Wipe away excess from tools, plug heads, membrane faces, pipework and surrounding surfaces while the material is still fresh. Once cured, Newtonite 801 Mastic can only be removed mechanically, with help from Soudal Sealant Remover Spray where suitable. Mechanical removal may involve careful cutting, trimming or scraping, so care is needed around damp proof membranes, finished surfaces, pipework and plug heads. Controlled application is always best, as preventing smears is easier than removing cured residue later.

Q) What are the limitations of Newton Newtonite 801 Mastic?

A) Newton Newtonite 801 Mastic should not be applied to wet, greasy, dusty, loose or unstable surfaces, as this can reduce adhesion and compromise the finished seal. It should not be used as a substitute for correct damp proof membrane design, correct fixing density or proper membrane installation. Its role is to seal fixing penetrations, plug heads, service entries and small detailing points, not to make an unsuitable membrane system work. It should also not be applied as a thin smear where a proper gasket or seal is required, because insufficient material may not accommodate movement or block moisture effectively. Preliminary compatibility tests are recommended on unusual plastics, coatings, paints or sensitive materials.

Q) What are the best tips for using Newtonite 801 Mastic successfully?

A) The best results with Newtonite 801 Mastic come from clean preparation, enough product and correct compression. Always remove drilling dust from around the pilot hole and wipe the membrane face clean before applying the mastic. When sealing plugs, apply a continuous ring rather than isolated spots, so the plug head compresses the mastic evenly and forms a full damp proof gasket. Do not wait until the mastic skins before inserting the plug, as the material needs to be uncured to compress properly. For service penetrations and recesses, fill the gap adequately and tool the surface before skin formation. Avoid over-smearing visible areas, and clean fresh residue immediately with Soudal Swipex Wipes.

Technical Data Sheet

Safety Data Sheet

Declaration of Performance (DoP)