Varistem vs BlastBags™
Your choice of stemming plug is a significant decision for mining and blasting consumables. You might be fighting flyrock on sensitive benches, or trying to
Your choice of stemming plug is a significant decision for mining and blasting consumables. You might be fighting flyrock on sensitive benches, or trying to cut explosive costs without inviting complaints about noise, vibration and airblast/over-pressure. In each case, the question is the same: how do you keep more energy in the rock without driving your cost per hole up or exceeding allowable environmental limits?
We compare Varistem and BLASTBAGS, both stemming solutions, on cost, hole-size coverage, explosive compatibility, mechanism, and real-world results.
Varistem prices increase with hole diameter, ranging from about $1 to $16.13 per plug. You can closely match plugs to actual hole diameters and push for better confinement and tighter cost-per-hole control across blast holes and rock types.
MTI’s BLASTBAGS are sold in cartons. Box size and price vary by diameter and application-based segmentation. Different BLASTBAG families, namely ACE, AERO, HERO, NERO, EVO, and ZERO, use per-bag pricing that rises with hole size.
Exact pricing for BLASTBAGS is typically in the low double digits per bag, often around US$8 to US$16, with the largest aerosol bags costing more than US$20 per unit.
Varistem is a low-cost stemming plug, typically in the US$1–16 (R17–R280) range, so you can tighten confinement and fragmentation without a big jump in cost per hole. MTI’s BLASTBAGS, by contrast, sit in a premium bracket at roughly US$8–16 per bag (and over US$20 for the largest aerosol units). BLASTBAGS are several times more expensive for certain hole diameters.
Varistem covers blasthole diameters from 1.75″ to 10″ (about 45 to 251 mm). Each plug size is designed for a specific diameter range, allowing you to match the plug closely to the actual drilled hole.
MTI’s BLASTBAG range is available for a wide range of blasthole sizes, typically from around 2.5″ up to 12¼″ (about 64 to 311 mm). However, this depends on the product family (ACE, AERO, HERO, Solo, NERO, or EVO).
Individual bag types are specified for overlapping-diameter windows. You can choose a gasbag that fits the drilled hole closely enough to create a reliable deck or stemming zone while still accommodating standard drilling tolerance.
Varistem provides tight, plug-by-plug sizing from 1.75″ to 10″, so you can match each stemming plug closely to the actual hole for consistent confinement. BLASTBAGS cover a broader overall range, from roughly 2″ up to 12¼″. Diameter coverage depends on the specific family and uses more expansive overlapping windows. In practice, Varistem gives finer control within its range, while BLASTBAGS extend coverage into larger diameters where you need gasbags for decking or specialised blast designs.
Varistem plugs are compatible with ANFO, emulsions and most standard commercial explosives. ANFO is preferred in dry holes, while emulsions, water gels or heavy ANFO are better suited to damp conditions. Varistem can also be used for air decking, allowing you to significantly reduce explosive consumption per blast.
BLASTBAGS work with common blasthole explosives, including bulk ANFO, pumped emulsions and cartridge products. The gasbags act as inert barriers rather than reactive components; they can be used in both dry and damp holes, above or between explosive decks. BLASTBAGS are suitable for both conventional full-column loading and air-decking designs.
Both Varistem and BLASTBAGS work with the full range of standard commercial explosives, including ANFO and emulsions, in dry or damp holes. Varistem offers a simple, lower-cost stemming plug that also supports basic air-decking to reduce powder factors.
Varistem uses a flexible, tear-resistant dip-moulded body. When the blast initiates, the first shock wave pushes the plug into the stemming, forming a temporary high-pressure seal in the hole. That seal forces more energy into existing microfractures, giving stronger early confinement, cleaner fragmentation and more efficient use of the explosive energy in the rock.
BLASTBAGS use an inflatable gas bag to create a confined air deck within the blasthole. Once positioned at the desired height, the bag is chemically inflated with aerosol or compressed air until it grips the hole walls and supports the stemming column above.
When the charge detonates, the gasbag and the air deck beneath the stemming act as a temporary, compressible barrier. They absorb and reflect the initial shock, reduce venting at the collar, and drive more energy into the surrounding rock and along the burden.
Varistem is a simple stemming plug that turns the first shock wave into a tight, temporary pressure seal inside the stemming. BLASTBAGS™, by contrast, are active gasbags that you inflate to build an air deck and support the stemming column, making them well-suited to air-decking and multi-deck designs where you want to shorten or separate explosive columns and still maintain good energy confinement.
Varistem has demonstrated an 11% uplift in advance per blast at an underground platinum mine (2.46 m to 2.82 m), translating to an estimated R1.91 billion annual net benefit. Additional studies report up to 80% less flyrock, 87% better cast, 14%+ higher crusher throughput, over $10 million per year in added value, $1.45 million in waste savings, and 8% quicker loading.
BLASTBAG performance is mainly documented through MTi’s own case studies rather than independent mine trials. The reported results are consistent across several sites. At a South American copper mine, air decking with BLASTBAGS reportedly cut ore loss by 36.6%, reduced powder factor by about 9.7%, improved fragmentation and saved roughly US$42,000 in recovery costs on the test blasts.
Vendor data suggests BLASTBAG air decking can improve fragmentation, limit flyrock and vibration, and lower explosive consumption.
Varistem’s benefits are supported by published mine trials and multi-site data, showing consistent gains in advance, reduced flyrock, better cast and higher crusher throughput, with clear links to annual financial upside. BLASTBAG results mainly come from vendor case studies, indicating that air decking with gasbags can reduce ore loss, lower the powder factor, and improve fragmentation, though with less independent verification than the Varistem plug data.
Choose Varistem when you need precise sizing and strong energy confinement across blastholes from 1.75″ to 10″ (about 45 to 251 mm). It is well-suited to operations where small gains in advance, crusher throughput or reduced flyrock translate directly into bottom-line improvement.
Varistem is a good choice for sites that value documented, field-proven performance and need a stemming solution that works reliably with ANFO, emulsions and air-decking designs.
Choose BLASTBAGS when air-decking and deck control are the main design goals, rather than simple stemming. They are a strong fit for long or large-diameter holes or sites where you want to shorten the explosive column, separate decks, or trial lower powder factors without losing energy confinement.
They are particularly useful where you already run ANFO/emulsion blends and want a purpose-built gasbag solution for complex multi-deck or optimisation work.
Varistem and BLASTBAGS are both great stemming options for different sites. Varistem gives you a low-cost, tightly sized stemming plug for everyday blasting. BLASTBAGS offer flexible air-decking and deck control at a higher unit cost, suited to specific benches or large-diameter holes.
Whichever way you lean, the value lies in matching the product to the problem. 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.
Your choice of stemming plug is a significant decision for mining and blasting consumables. You might be fighting flyrock on sensitive benches, or trying to
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The purpose of the Varistem® stemming plug trial conducted at Coal Mine X was to reduce flyrock, noise, and airblast by retaining blast energy. The