Every blasting job in Trinidad eventually comes down to one question: what goes in the pot? The two workhorses — garnet and copper slag — solve different problems, and picking wrong costs you money on every square metre. Here is how we advise our customers to decide.
The short answer
Use copper slag when the job is big, open-air, single-use and the steel is heavily scaled — structural work, tank externals, barge hulls where reclaim is impractical. Use garnet when you can recover the media, when the spec calls for a tight profile window, or when you are working near equipment that will not tolerate embedded contamination — machined surfaces, stainless, ballast tanks, anything going under high-performance coatings.
Cutting speed vs. total cost
Copper slag is cheap per bag and cuts fast on heavy mill scale — that is why it dominates one-pass yard work. But it is a single-use expendable: once it hits the deck it is contaminated waste, and disposal is part of your real cost. Hard-rock garnet costs more upfront and can be reclaimed up to four times with proper screening. On enclosed jobs with recovery — blast rooms, contained scaffolding wraps — garnet's cost per blasted square metre routinely beats slag by the second cycle.
Profile control
Coating specifications increasingly demand a defined anchor profile — 50–75 µm is the common window for high-build epoxies. Garnet's hardness (7.5–8 Mohs) and consistent grading hold that window reliably at 90 psi. Slag profiles run deeper and rougher, which suits some primers but risks peaks poking through thin-film systems, the classic cause of premature rust rash on "freshly painted" steel.
The silica question
Neither garnet nor copper slag is a silica-sand substitute problem — both run below 1% free silica, and crushed glass is 0%. If any supplier offers you beach or river sand for blasting, walk away: silicosis is permanent, and modern HSE regimes (including the STOW requirements most T&T energy clients enforce) treat sand blasting as a prohibited practice.
What we stock
GML is the authorized Rockridge distributor for Trinidad & Tobago: garnet 30/60 and 20/40, copper slag 30/60, steel grit G40, aluminium oxide, glass beads and crushed glass — all in 25 kg bags, on-island, with volume pricing at 10, 50 and 100+ units. If you are unsure what your spec needs, send it to us — our NACE/AMPP-certified inspectors read coating specs for a living.