Varistem Stemming Plug vs RockRivet
In blasting, every metre of advance and every ton of ore or aggregate matters. Mines, quarries, and construction crews face daily challenges: uneven breakage, flyrock,
Blasts that lose containment energy drive up costs. The stemming plug you choose directly impacts how productive each blast becomes.
We compare Varistem and Max-Blast stemming plugs on cost, diameter coverage, explosive compatibility, and mechanism, using available evidence, to help you choose.
Varistem prices increase with hole diameter, ranging from about $1 to $16.13 per plug (R17 to R280). You can closely match plugs to actual hole diameters and push for better confinement, more consistent fragmentation, and tighter cost-per-hole control across very different blast holes and rock types.
Max-Blast plugs are priced by hole diameter, typically ranging from about $2.49 to $7.20 (roughly R43 to R123) per plug. This places them in a mid- to upper-cost bracket and means per-hole stemming costs should be carefully factored into overall blast budgeting, especially on large blasting sites.
Varistem plugs follow a strict diameter-based price ladder, from about $1.00 for the smallest sizes up to $16.13 for 10″ holes, making costs predictable and easy to budget. Max-Blast plugs start at $1.48, with heavier or rigid models priced at $7.70.
Unlike Varistem, the pricing of Max-Blast stemming plugs depends more on rigidity than on exact hole diameter, adding complexity.
Varistem plugs are available for blastholes from 1.75″ up to 10″ in diameter (roughly 45–251 mm). Each size is engineered for a defined diameter range.
Max-Blast stemming plugs cover hole diameters from 1½″ to 6″ (approximately 38 to 152 mm), with multiple sizes available to match common drill patterns.
For operations where every hole must be tightly matched, such as in hard rock mines aiming for maximum energy confinement, Varistem’s fine-size ladder delivers predictable, repeatable fits across diameters from 1.75″ to 10″. For operations drilled in standard 1½″ to 6″ holes, Max-Blast plugs use fewer, broader size bands rather than a fine-size ladder, so each plug is designed to fit a wider range between 1½″ to 6″.
Varistem plugs work with ANFO, emulsions and most standard commercial explosives. In dry holes, ANFO is recommended; in damp conditions, an emulsion, water gel or heavy ANFO is more suitable. Varistem can also be used for air-decking, significantly reducing the amount of explosive needed per blast.
Max-Blast stemming plugs are mechanical vinyl plugs that sit above the explosive column, making them generally compatible with standard commercial explosives. The manufacturer states use with expanding (gassed) explosives, where the explosive rises to the plug after it has been set, in vertical or horizontal holes.
Varistem stemming plugs are broadly compatible with ANFO, emulsions, and most commercial explosives, with clear guidance on dry vs. damp holes and the option of air-decking to reduce explosive consumption.
Max-Blast plugs are also generally compatible with standard explosives, with a particular emphasis on expanding (gassed) explosives in vertical, horizontal and up-holes, where the mechanical vinyl plug helps confine the rising column.
Varistem offers better stated overall explosive compatibility.
Varistem uses a flexible, tear-resistant dip-moulded shell. When the charge fires, the initial shock wave drives the plug into the stemming to create a temporary pressure seal in the hole, directing energy into existing microfractures before the plug fails. This provides stronger early confinement, cleaner fragmentation and more efficient use of explosive energy in the rock.
Max-Blast plugs use a flexible vinyl body with a patented accordion profile that installs as a simple friction-fit in the borehole. Once pushed to depth with a loading pole, the plug grips the hole wall and holds the stemming above the explosive. With the stemming column locked in place, more of the blast energy is driven into the surrounding rock, improving confinement and fragmentation while helping to cut flyrock, airblast, dust and vibration.
Varistem relies on a shock-driven, sacrificial plug that briefly locks in pressure for stronger early confinement, while Max-Blast stemming plugs use an accordion-style friction-fit plug that locks the stemming in place to improve fragmentation and reduce flyrock, airblast, dust and vibration.
Varistem’s performance is backed by field results. In an underground platinum mine trial, it delivered a consistent 11% increase in advance per blast, raising average advance from 2.46 m to 2.82 m and generating an estimated annual net benefit of R1.91 billion through improved ore recovery.
Across different sites, Varistem has been credited with up to 80% less flyrock, 87% better cast, more than 14% higher crusher throughput, over $10 million per year in additional value, $1.45 million in savings from reduced waste, and loading rates up to 8% faster in reported studies.
Max-Blast plug results are mainly reported through vendor and distributor claims rather than published trials. Vendor information states that Max-Blast stemming plugs can improve fragmentation by 20 to 40% while reducing flyrock, airblast, dust, and vibration in both surface and underground blasting. No mine-specific performance data or independent cost-benefit studies are published alongside these figures.
Varistem’s impact is supported by quantified mine trials and documented financial gains. Max-Blast reported benefits are vendor claims, and do not include published, mine-specific, or independently verified performance data. Varistem is therefore clearly better researched, with stronger overall flyrock mitigation.
Choose Varistem when you need larger sizing control and maximum energy confinement across a wide range of hole diameters, from 1.75″ to 10″ (about 45 to 251 mm). It is a strong fit where every extra per cent of advance, crusher throughput, or reduced flyrock translates into measurable financial gain.
Varistem suits sites that want documented, field-proven performance, compatibility with ANFO, emulsions and air-decking.
Choose Max-Blast plugs when your drilling is concentrated in standard 1½″ to 6″ (around 38 to 152 mm) blast holes. Max-Blast stemming plugs are well-suited to quarries, construction sites, and mines that rely on a small set of common hole sizes and want a mechanical plug that works easily with gassed or other commercial explosives in vertical, horizontal, or up-holes applications.
A well-chosen stemming plug can turn the same blasting hole and explosive column into a safer, cleaner and more productive blast. The product choice depends on which size fits your blast holes, explosives, budget and risk profile best.
Varistem is generally the stronger option for most mines and quarries, especially where you’re working with high-value ore, hard rock or a mix of hole diameters from about 1.75″ to 10″ and want better energy containment. Max-Blast stemming plugs are a good fit if your drilling is concentrated in standard 1½″ to 6″, with better in-between sizes.
ERG Industrial offers in-depth advice on stemming plugs and other blasting equipment. Contact us for a quote to see how your blasting team can benefit from Varistem.
In blasting, every metre of advance and every ton of ore or aggregate matters. Mines, quarries, and construction crews face daily challenges: uneven breakage, flyrock,
In our business, we are in a unique position where we get to spend time at countless sites, working with drillers and blasters during the planning,
Blasts that lose containment energy drive up costs. The stemming plug you choose directly impacts how productive each blast becomes. We compare Varistem and Max-Blast