A stemming solution is often overlooked in blasting, yet it has an outsized effect on the result. When stemming fails, and that energy escapes, the consequences can have a negative impact on a site’s profits. Varistem and STEMGEL LRC take two fundamentally different approaches.
Varistem is a physical stemming plug that is inserted and installed into the hole. STEMGEL is a liquid reagent that is pumped into the hole with water, where it sets into a solid hydrogel stem deck. We compare their cost models, deployment, hole compatibility, and other important factors, providing staff with the information needed to choose the option that best fits their site.
Varistem plug prices scale with hole diameter, ranging from approximately US$1 for smaller sizes up to around US$16.13 for the largest. You pay only for the size the hole requires, which keeps the cost per hole predictable across blast patterns with varying hole diameters. Pricing is published and diameter-based, allowing it to be budgeted at the planning stage.
STEMGEL is a concentrated liquid reagent (LRC) and not a per-unit consumable like stemming plugs. Shockwave Gel Technologies does not publish unit or per-hole pricing. Costs are worked out per operation based on hole dimensions, dose rate, and the dosing equipment used.
The supplier positions it as more cost-effective than aggregate stemming, but without published information, direct comparison with a plug is not possible.
The two products can’t be compared on a like-for-like unit price because they are priced on different models. Varistem has published diameter-based pricing, and STEMGEL pricing is quote-only and operation-specific. It also requires dedicated GELDRIVE dosing equipment to load, which Varistem does not.
For procurement teams that need a clear up-front number, Varistem is more transparent. However, if you’re willing to obtain pricing and use proprietary equipment for STEMGEL, it can be cost-effective in certain scenarios.
Varistem is available for blasthole diameters from 1.75 inches (45mm) to 10 inches (251mm). The full lineup covers that range with dedicated plug sizes, each closely matched to a specific diameter window, providing a precise fit for most standard production hole diameters.
STEMGEL LRC is a pumped gel that conforms to the hole rather than being matched to a specific diameter. It is supplied for down-hole and above-hole stemming in open-cut mining and civil applications. The GELDRIVE dosing units deliver the gel into the hole and can pump from up to 50 metres from the truck.
Varistem offers a discrete, documented size for each diameter window, which makes plug-to-hole matching precise and easy to specify. STEMGEL’s sizing is completely based on the hole it is pumped into, which offers a benefit in irregular or varied holes.
Varistem works alongside the full range of commonly used commercial explosives: ANFO, emulsions, heavy ANFO, and water gels. Explosive selection is driven by hole conditions and site practice as normal, with ANFO suited to dry holes and emulsion or water gel preferred where water is present.
STEMGEL is stated as suitable for use with emulsions, and water gels. Any contact with water renders ANFO non-explosive, as ammonium nitrate is highly soluble; since STEMGEL uses water, it may be incompatible.
Varistem documents compatibility across the specific commercial explosive families. STEMGEL LRC claims compatibility with water gels and emulsions. However, in the case of ANFO, it may be incompatible, meaning Varistem would be compatible with more explosives.
Varistem is placed point-down into the blasthole, resting directly on top of the explosive column. Stemming material is loaded above it as normal. On detonation, the initial shockwave forces the plug upward into the stemming column, where its flexible, tear-resistant body wedges against the blasthole wall and forms a temporary pressure seal. That seal holds long enough to redirect more explosive energy into the surrounding rock before the flame front destroys the plug.
STEMGEL LRC is pumped into the hole hose-in-hose with water, where the reagent and polymer blend invert to form a solid hydrogel set in place as a stem deck coupled to the explosive.
On initiation, the gel deck attenuates the pressure shockwave, compressing and reflecting energy into the formation to minimise energy loss and increase fragmentation. The gel is then ejected as water vapour, producing lower air overpressure, noise, and dust.
Both work on the same blast principle of confining and reflecting energy, but deployment is completely different. Varistem drops into the hole, ready to use with no preparation and no special equipment.
STEMGEL LRC requires GELDRIVE dosing equipment and a water supply to pump and set the gel, which is a larger up-front commitment but removes the need to handle and haul aggregate stemming and can reduce or eliminate the need for personnel on the blast floor.
Varistem publishes independently verified case study results across multiple site types. At one underground platinum mine, advance per blast improved from 2.46 m to 2.82 m, a gain of around 15%, with the associated case study estimating an annual net benefit of R1.91 billion linked to improved ore recovery.
Other documented outcomes include flyrock reductions of up to 80%, an 87% improvement in cast, crusher throughput gains of more than 14%, loading rate improvements of up to 8%, more than US$10 million per year in added value, and approximately US$1.45 million in savings from reduced waste blasts.
Shockwave states that STEMGEL LRC delivers increased rock fragmentation, lower air overpressure, and reduced noise and dust compared with aggregate stemming. According to the company, the gel absorbs up to 98% of the blast-pressure shockwave, reflecting it back into the formation as a tension wave of almost equal force, thereby substantially increasing microfracturing and breakage.
Shockwave maintains a library of data, photos, and videos available to licensees and distributors upon request, but quantified field results are not published publicly.
Both suppliers make strong performance claims. The difference is in public evidence. Varistem publishes independently verified, quantified case study data across multiple sites.
STEMGEL LRC’s headline figures come from the manufacturer, with supporting data held privately for licensees rather than published.
Choose Varistem stemming plugs when you want a straightforward, cost-effective stemming solution with a proven track record and transparent performance data. It covers blasthole diameters from 1.75″ to 10″, and fits the full range of standard commercial explosives.
These stemming plugs need no special loading equipment and drop into the hole ready to use. Varistem suits operations that value documented results, simple deployment, and predictable per-hole costs.
Choose STEMGEL LRC when your operation can support dedicated dosing equipment and wants to move away from entirely relying on aggregate stemming. Its gel system suits wet, hot, or dynamic water holes and can reduce dust and noise on the blast floor. It is a strong fit for open-cut and civil operations, prioritising blast-control consistency and operational efficiency at scale.
Varistem and STEMGEL LRC solve the same problem in very different ways. Varistem is a simple, ready-to-use plug with transparent, diameter-based pricing, a fully documented size range, independently verified results, and no special equipment required for deployment.
STEMGEL LRC replaces aggregate stemming with a pumped hydrogel and is suited to larger open-cut and civil operations under difficult water or temperature conditions, and to infrastructure that supports GELDRIVE dosing.
Ultimately, the decision comes down to your operations’ needs, with both offering beneficial outcomes in the right setting. Contact us to get a quote for Varistem stemming plugs.
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