PlastiSeal®
STP's one-part flexible crack sealer — a white thixotropic paste that cures yet stays flexible to seal small masonry cracks.
PlastiSeal® at a glance
The essentials specifiers and contractors ask first — answered straight from the product data, with links to go deeper.
What is it?
PlastiSeal® is STP Limited's one-part flexible crack sealer, supplied as a ready-to-use white thixotropic paste. It cures but remains flexible, so the repair moves with the substrate and reseals small cracks against water rather than re-fracturing like a rigid filler.
Where is it used?
Per STP's TDS, PlastiSeal is intended for internal and external masonry wall cracks. It is applied straight from the container into clean, pre-dampened cracks that have been opened into a V-groove where possible.
Why use it?
It stays flexible after cure and is waterproof, so it accommodates the small thermal and structural movement that causes hairline masonry cracks to keep re-opening. Being a one-part paste, it needs no mixing, has a long working window and is simply thinned with water for hairline penetration.
How is it applied?
Clean the crack to sound substrate, widen it into a V-groove where possible, pre-dampen for adhesion, then work the paste in with a spatula or putty knife and level flush. Deep cracks may shrink and need a second pass; hairline cracks are thinned with potable water to penetrate. Full cure takes 7 days. Always follow the current STP TDS.
Key advantages
- Cures yet stays permanently flexible, so the repair moves with the wall instead of re-cracking like a rigid filler
- One-part and ready to use — no mixing, no catalyst, no proportioning errors, and a long, unhurried working window
- Thixotropic paste holds its shape in vertical and overhead cracks without slumping
- Water-thinnable: neat for normal cracks, thinned with potable water to penetrate fine hairline cracks
- Waterproof once cured, helping keep sealed cracks closed against water ingress
- Excellent chemical resistance when fully cured — to water, gasoline, oil and salts (5% calcium chloride)
- Cleans up with water before the material hardens, simplifying tools and site housekeeping
- Long 12-month shelf life in the unopened 1 kg pack for easy stocking on small repair jobs
Specifications
- Product type: One-part flexible crack sealer (white thixotropic paste)
- Physical appearance: White thixotropic paste
- Application area: Internal and external masonry wall cracks
- Chemical resistance (fully cured): Excellent — water, gasoline, oil and salts (5% calcium chloride)
- Full cure: 7 days
- Mixing: Requires no pre-mixing; use directly from the container, thin with potable water for hairline cracks
- Packaging: 1 kg pack
- Shelf life: 12 months in original unopened sealed condition
- Storage: Cool, dry place, under shed, away from heat
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About PlastiSeal®
A plain-language overview of what PlastiSeal® is, the problem it solves and how Space Arc Engineering positions it in a specification.
PlastiSeal® is a flexible crack-sealing paste from STP Limited (formerly Shalimar Tar Products, now part of the Berger group). It is a one-part, ready-to-use white thixotropic paste that is applied directly from the container — no pre-mixing, no catalysts and no on-site proportioning. Once placed, it cures but retains permanent flexibility, which is the whole point of the product: small masonry cracks are rarely static, and a sealant that can stretch and recover with the wall keeps the crack closed where a hard, rigid filler would simply de-bond or split again.
STP positions PlastiSeal specifically for internal and external masonry wall cracks. The paste is thixotropic, so it holds its shape in a vertical or overhead crack without slumping, yet can be thinned with clean potable water when a hairline crack is too fine to take the neat material. After full cure it is waterproof and, on STP's published testing, shows excellent resistance to water, gasoline, oil and salts (5% calcium chloride) — useful where a sealed crack is later exposed to weather, splashing or de-icing/road salts.
As a distributor, Space Arc Engineering supplies PlastiSeal in its 1 kg pack and advises on where it is the right choice versus STP's cement-based sibling, PlastiSeal P. PlastiSeal is the flexible, movement-accommodating option for small cracks; PlastiSeal P is a separate cementitious polymer-modified powder used as a slope leveller and crack filler for wider, more static repairs. Getting that distinction right at the specification stage avoids the common failure of using a rigid filler in a crack that keeps moving.
The technical insight
Why PlastiSeal® behaves the way it does — the mechanism behind the performance, in specifier-friendly terms.
PlastiSeal works as a flexible, polymer-based sealing paste rather than as a cementitious mortar. Because it is a thixotropic paste, it stays put in the crack during application and then films and cures while keeping an elastic, rubber-like character — so when the wall expands and contracts with daily and seasonal temperature swings, the sealed crack can open and close slightly without the repair cracking through or losing bond. This is the fundamental difference from a hard cement-based filler, which has little movement capacity and tends to re-crack at the same line. The one-part chemistry also means there is no pot-life clock to race against on site: the material is used straight from the tin and only adjusted with water for workability.
Where PlastiSeal® is used
Typical applications PlastiSeal® is specified for, supplied by Space Arc Engineering across Delhi NCR, Ghaziabad, Noida and Uttar Pradesh.
- Sealing internal masonry wall cracks
- Sealing external masonry wall cracks
- Filling small/hairline cracks that are subject to minor thermal movement
- V-grooved crack repair on plastered and masonry walls
- Flexible sealing of fine cracks thinned with water for deeper penetration
- Crack repairs where waterproofing and chemical (oil/salt) resistance are needed after cure
Key advantages
The properties that make PlastiSeal® the right choice — drawn from the manufacturer's product literature.
- Cures yet stays permanently flexible, so the repair moves with the wall instead of re-cracking like a rigid filler
- One-part and ready to use — no mixing, no catalyst, no proportioning errors, and a long, unhurried working window
- Thixotropic paste holds its shape in vertical and overhead cracks without slumping
- Water-thinnable: neat for normal cracks, thinned with potable water to penetrate fine hairline cracks
- Waterproof once cured, helping keep sealed cracks closed against water ingress
- Excellent chemical resistance when fully cured — to water, gasoline, oil and salts (5% calcium chloride)
- Cleans up with water before the material hardens, simplifying tools and site housekeeping
- Long 12-month shelf life in the unopened 1 kg pack for easy stocking on small repair jobs
Limitations & considerations
Where PlastiSeal® is not the right answer. Check these constraints from the manufacturer before specifying — using it outside its scope is the most common cause of failure.
- It is a sealer for small/hairline masonry cracks, not a structural repair — it does not restore strength and is not a substitute for crack-stitching, grouting or grout-injection on live structural or load-bearing cracks.
- STP's TDS does not state a maximum crack width; very wide, deep or actively moving cracks and true expansion/movement joints need a backer rod and a dedicated joint sealant, not a sealing paste.
- It is a paste, not a cementitious filler — for slope levelling or filling wider, more static cracks STP's separate cementitious product PlastiSeal P is the intended choice.
- Performance depends on preparation: surfaces must be clean and sound and the crack pre-dampened, otherwise adhesion suffers. Deep cracks shrink on cure and must be filled in repeated passes.
- Overcoating with a particular waterproofing membrane and any standards/IS-ASTM compliance are not stated in the official TDS — confirm compatibility and approvals with the TDS or with us before specifying over-coating.
Selection & best practice
How to decide whether PlastiSeal® fits your job — and how to apply it so the repair lasts.
Specify PlastiSeal when you need to seal small, non-structural masonry wall cracks that are subject to minor thermal or structural movement and you want a sealant that will flex rather than re-crack. Choose it over a rigid cement-based filler precisely where movement is expected. Where the crack is wide, deep, static or you need slope levelling, move to the cementitious PlastiSeal P instead; where the gap is a genuine movement/expansion joint, use a backer rod with a proper joint sealant. For live structural cracks, treat the cause and use a structural repair system, not a sealing paste.
Application best practice
- Prepare to sound substrate: remove oil, dirt, debris, paint and any bond-breaker, finishing with vacuuming or pressure-washing so the crack is clean.
- Open the crack into a V-groove wherever possible to give the sealant a sound key and adequate cross-section.
- Pre-dampen the crack before placing the paste — the TDS calls for a damp (not flooded) crack for proper adhesion.
- Apply neat with a spatula or putty knife and level flush; for fine hairline cracks where widening is not possible, thin with clean potable, soft water to aid penetration.
- Expect shrinkage in deep cracks — re-apply in successive passes until the crack is filled level rather than over-filling in one go.
- Clean tools and equipment with water before the material hardens, and allow the full 7-day cure before exposing the repair to demanding service.
Specifications
Indicative properties from the manufacturer's literature. Always confirm batch-specific values against the current TDS before specification.
| Product type | One-part flexible crack sealer (white thixotropic paste) |
|---|---|
| Physical appearance | White thixotropic paste |
| Application area | Internal and external masonry wall cracks |
| Chemical resistance (fully cured) | Excellent — water, gasoline, oil and salts (5% calcium chloride) |
| Full cure | 7 days |
| Mixing | Requires no pre-mixing; use directly from the container, thin with potable water for hairline cracks |
| Packaging | 1 kg pack |
| Shelf life | 12 months in original unopened sealed condition |
| Storage | Cool, dry place, under shed, away from heat |
Coverage, dosage, pack sizes and cure times vary with substrate and conditions — request the full TDS for certified technical data.
Industry use cases
Real-world scenarios where PlastiSeal® is the practical choice — the teams who reach for it and the jobs it does for them.
- Residential and commercial buildings — sealing recurring hairline cracks in internal and external plastered masonry walls
- Building maintenance and facility upkeep — routine flexible crack sealing where rigid fillers have previously re-cracked
- Industrial premises — sealing wall cracks in areas exposed to oils, fuels or salt where cured chemical resistance is valued
- Pre-decoration repair on masonry walls where small movement cracks need a flexible seal before finishing
Frequently asked questions
Common questions about specifying and sourcing PlastiSeal®.
What exactly is PlastiSeal and what is it made of?
It is STP's one-part flexible crack sealer, supplied as a ready-to-use white thixotropic paste. It is not a cement-based filler — it is applied straight from the container and cures while staying flexible so it can move with the wall.
What cracks is it meant for?
STP's TDS specifies internal and external masonry wall cracks. It is best for small and hairline cracks subject to minor thermal or structural movement; it is not a structural repair and is not intended for wide, deep or actively moving cracks or for movement/expansion joints.
How is PlastiSeal P different from PlastiSeal?
PlastiSeal is the flexible paste that stays elastic after cure. PlastiSeal P is a separate cementitious, polymer-modified powder used as a slope leveller and crack filler for wider, more static repairs. Use PlastiSeal where movement is expected and PlastiSeal P where you need a cement-based fill or levelling.
Does it need mixing, and how is it applied?
No mixing is needed. Clean the crack to sound substrate, open it into a V-groove where possible, pre-dampen it, then work the paste in with a spatula or putty knife and level flush. For very fine hairline cracks, thin it with clean potable water to help it penetrate. Deep cracks shrink and may need a second pass.
How long does it take to cure and how is it cleaned up?
Full cure is 7 days per the TDS. Clean tools and equipment with water before the material hardens.
Is it waterproof and chemically resistant?
Yes — STP lists it as waterproof once cured, with excellent resistance on fully cured samples to water, gasoline, oil and salts (5% calcium chloride).
What pack size is available and how do I get pricing and the TDS?
PlastiSeal is supplied in a 1 kg pack with a 12-month shelf life unopened. Space Arc Engineering is a distributor for STP Limited — contact us for current pricing, stock and the latest Technical Data Sheet and MSDS.
References
Manufacturer and technical sources this page draws on. Always confirm current data against the live TDS before specification.
Source PlastiSeal® for your project
Space Arc Engineering is an authorised distributor for STP, serving Delhi NCR, Ghaziabad, Noida and Uttar Pradesh. Talk to us for pricing, the technical data sheet and on-site support.
Or email info@space-arc.com · www.space-arc.com