NextStar #4 ULV Epoxy — Ultra-Low Viscosity for Hairline Concrete Cracks
2:1 Ultra-Low Viscosity Epoxy for Gravity Feeding and Low-Pressure Injection — The Thinnest Epoxy Available, Works on Damp or Wet Concrete
The thinnest epoxy available — penetrates hairline cracks standard LV epoxy cannot reach
Gravity feeding or low-pressure injection into ultra-fine cracks
100% solids — water-insensitive, bonds to damp or wet concrete
40 CPS mixed viscosity — thinner than most motor oils
Up to 60-minute working time — extended penetration into the finest cracks
Horizontal, vertical, and overhead surfaces
Gravity-feed repair for specialty concrete and stone structures
Rusted snap-tie holes and micro-voids in poured concrete
Structural cure — 12,000 PSI compressive, bond strength meets ASTM C-882
Several packaging options — 450ml tube sets to 3-gallon jugs
Free NextStar Technical Support — 1-866-445-3984
Ships USA & Canada
What Makes ULV Different — Viscosity Thin Enough for Hairline Cracks
NextStar #4 is a 2:1 ratio ultra-low viscosity (ULV) two-component epoxy formulated for cracks too fine to accept standard low-viscosity epoxy. At just 40 CPS mixed — thinner than most motor oils — it is the thinnest epoxy available and flows into hairline cracks, micro-voids, and rusted snap-tie holes that standard 1:1 LV epoxy cannot penetrate.
This is supplied as the epoxy material itself, in your choice of packaging — not a kit. It is the right product when you already have an injection tool, are doing repeat or contractor-volume work, or need ULV epoxy for gravity-feed and specialty applications. If you want a complete single-job package with injection ports and everything included, see the 10ft DIY ULV Auto-Injector Epoxy Kit instead.
NextStar #4 is 100% solids and water-insensitive, so it bonds effectively to damp or wet concrete — a critical advantage when injecting cracks exposed to moisture or groundwater. It cures into a structural repair: it bonds the crack faces together and restores the concrete's strength, not just its water resistance.
60-Minute Working Time — Deep Penetration Through Fine Cracks
The extended working time is intentional. ULV epoxy has to travel deep through extremely fine crack networks before it gels, and the slow chemistry gives it the time to reach the full depth of the crack. Standard epoxies gel in about 20 minutes, which is often too fast for the slowest-penetrating cracks.
Working time depends on volume and temperature. In larger mixed volumes, the maximum working time is about 30 minutes; in small volumes or cooler conditions, it stays workable considerably longer, 60 minutes or more. One practical note: keep larger mixed volumes moving and injecting rather than sitting in the pot — a large static mass of epoxy generates its own heat (an exothermic reaction) that accelerates the cure, so injecting steadily keeps the material thin and workable for longer.
Gravity Feed vs Low-Pressure Injection — Two Application Methods
Low-pressure injection is used for cracks in vertical walls and overhead surfaces, where ports are attached over the crack and the epoxy is injected through them. A spring or pneumatic injection tool is recommended for this material — it holds steady pressure between strokes, which matters for ultra-fine cracks where the epoxy flows slowly and benefits from sustained injection time. NextStar #4 works with any standard 2:1 dual-cartridge injection tool; there is no proprietary tool to buy, and a cartridge tool or dual-cartridge tool can be added with your order.
Gravity feeding flows the epoxy into a crack from above and lets gravity carry it down through the crack, with no pressure equipment. It is used on horizontal surfaces such as floor slabs and flat deck cracks, and for repairing or bonding specialty concrete and stone structures. The ultra-low 40 CPS viscosity is what makes #4 one of the few epoxies that gravity-feeds effectively into fine cracks. It can also be mixed with aggregate and used as a grouting resin.
#4 ULV vs Standard LV Epoxy — When Ultra-Low Matters
The injectable crack ranges of the two epoxies overlap, so the question is not strictly crack width — it is whether standard LV epoxy can actually penetrate your crack. NextStar #4 is the thinnest epoxy available, so it is the choice whenever a crack is too fine, too tight, or too slow for standard 1:1 LV epoxy to fill completely.
| Use |
Product |
| Hairline and ultra-fine cracks, rusted snap-tie holes, micro-voids, gravity feed, damp concrete |
NextStar #4 ULV (this product) |
| Standard structural cracks where LV epoxy penetrates fully, 1/32 to 3/8 inch wide |
Standard LV-121 Epoxy Kit → |
| Complete single-job DIY kit with auto-injector ports and tool included |
10ft DIY ULV Auto-Injector Kit → |
NextStar #4 Technical Specifications
Physical Properties — Components A and B
Solids: 100% (both components)
Mix Ratio: 2:1 by volume (A:B)
Mixed Viscosity: 40 CPS at 77°F — ultra-low
Shelf Life: 1 year from manufacture date
Application
Working Time (larger volume): up to 60 minutes at 77°F (longer in small volumes or cool conditions)
Lowest Cure Temperature: 40°F (10°C)
Full Cure: approximately 4 days
Methods: gravity feed or low-pressure injection
Can be mixed with aggregate as a grouting resin
Cured Performance
Compressive Strength: 12,000 PSI
Bond Strength to Concrete: meets ASTM C-882
100% solids, water-insensitive
Packaging Options
NextStar #4 is supplied as the epoxy material in several quantities. The base offering is a 450ml dual-cartridge tube set (2:1 ratio), which requires an application tool. Larger mini-bulk jug formats are available for mix-by-hand or high-volume work. Tool and jug options can be selected with your order:
450ml dual-cartridge tube set (base) — requires an application tool
Optional cartridge tool or dual-cartridge tool
1.5 quarts (2.8 L) in jugs — mix by hand
3 gallons (11 L) in jugs — high-volume / contractor
The recommended mixer for this epoxy is the 1/4 x 32 static mixer. Call 1-866-445-3984 to confirm the right packaging and applicator for your repair.
Surface Preparation
Surfaces must be clean and sound — free of dust, sealers, grease, and other bond-inhibiting contaminants. For injection, entry ports should be approved devices spaced at intervals that allow full penetration of the resin. For gravity-feed applications, the surface above the crack must be clean so the epoxy flows downward without obstruction. The concrete must be at least 40°F (10°C) for proper cure.
Common Questions About NextStar #4 ULV Epoxy
What makes NextStar #4 different from standard LV epoxy?
NextStar #4 is a 2:1 ratio ultra-low viscosity epoxy at 40 CPS mixed — the thinnest epoxy available and significantly thinner than standard 1:1 LV-121 epoxy. This lets it penetrate cracks too fine for standard injection epoxy. It also has a longer working time, giving the epoxy more time to travel deep into ultra-fine crack networks before gelling.
What cracks is NextStar #4 designed for?
Hairline and ultra-fine cracks, rusted snap-tie holes, and micro-voids where standard low-viscosity epoxy cannot penetrate. The injectable ranges of the two epoxies overlap, so the deciding factor is penetration: choose #4 whenever a crack is too fine or too tight for standard LV epoxy to fill completely. It is also used for gravity-feed repairs and as a grouting resin when mixed with aggregate.
Can it be applied to wet or damp concrete?
Yes. NextStar #4 is 100% solids and water-insensitive, so it bonds effectively to damp and wet concrete surfaces — suitable for cracks exposed to moisture or groundwater infiltration. Bond strength to concrete meets ASTM C-882.
What is gravity-feed injection and when is it used?
Gravity feeding flows the epoxy into a crack from above and lets gravity pull it down through the crack with no pressure equipment. It is used on horizontal surfaces such as floor slabs and flat deck cracks, and for repairing specialty concrete and stone structures. The ultra-low 40 CPS viscosity makes #4 one of the few epoxies that can gravity-feed effectively into fine cracks.
What injection tool works best with NextStar #4?
A spring or pneumatic injection tool is recommended because it holds steady pressure between strokes, which improves penetration on ultra-fine cracks where the epoxy flows slowly and benefits from extended injection time. NextStar #4 works with any standard 2:1 dual-cartridge injection tool — there is no proprietary tool required, and a cartridge or dual-cartridge tool can be added with your order. Call 1-866-445-3984 to confirm the right setup.
How long is the working time, and why does it vary?
Up to about 30 minutes at 77°F in larger mixed volumes, and longer in small volumes or cooler conditions. Keep larger mixed volumes moving and injecting rather than sitting in the pot — a large static mass of epoxy generates its own heat (an exothermic reaction) that speeds the cure, so steady injection keeps the material thin and workable longer.
Does NextStar #4 require a minimum concrete temperature?
Yes. The concrete must be at least 40°F (10°C) for proper cure. For repairs in cold conditions, warm the cartridges before use to improve flow. Full cure takes approximately 4 days.
What packaging options are available?
The base is a 450ml dual-cartridge tube set (2:1 ratio), which requires an application tool. Larger mini-bulk options include 1.5-quart and 3-gallon jugs for mix-by-hand or high-volume work. A cartridge tool or dual-cartridge tool can be added with your order. The recommended mixer is the 1/4 x 32 static mixer.
Can the repaired area be painted or coated after curing?
Yes. After full cure at approximately 7 days, the repaired area can be painted, coated, or finished as required. Ensure the surface is clean and free of any uncured epoxy residue before applying coatings.
Questions about whether NextStar #4 is the right product for your crack? Call our free technical support line at 1-866-445-3984 — our team will confirm the correct epoxy, packaging, and applicator for your repair.
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