thousands of growers
tell the story

All images are from independent growers posting positive results after using OSA/28.

Of course we'll say OSA/28 is amazing.
Listen to growers like you instead.

About Orthosilicic acid

Silicic acid is very important for optimal plant health. Countless studies over the last couple decades from around the world show how silicic acid helps growers build stronger plants, optimize crop nutrition, plus increase yields and quality.

Stabilized orthosilicic acid is a small group of silicic acid molecules suspended in solution. When added to water, these molecules break apart into monomer form -- this is how silicon becomes immediately and rapidly available to plants!

We didn't invent silicic acid, nature did. Hell, we weren't even first to market. We're just trying to be the best...that's what growers need.

"Being first isn't the point, being the best is."
- Stephen Fry

Orthosilicic acid is badass

Faster Growth

Under fast growth conditions like indoor gardening, plants need constant resupply of essential elements. Every second nutrients are unavailable slows growth. Silicic acid works in many ways listed here to increase the transport and utilization of minerals, proteins and transports systems to ramp up growth.

Tighter Node Spacing

Countless studies show silicic acid affecting plant structure. It's one of the most visible and quickest effects growers report. Silicic acid builds more rigid and compact cells. It also helps convert more nitrates into proteins, which impacts node spacing and increases flowering sites.

Increased Nutrition

As silicon accumulates in cell walls, it concentrates and hardens. The nutrient transport system (xylem/phloem) is strengthened and expanded, increasing sap pressure and making heavier nutrients like calcium move better through the plant. More nutrients mean more essential building blocks.

Greater Yields

All plants accumulate silicon to some degree. Rice for example, up to 10% of dry weight! Flowering plants like tomatoes and cannabis closer to 2-3%. Since silicon is twice as heavy as nitrogen and almost 3x carbon, a small amount of silicon contributes to large gains in yield.

Stress Resistance

Silicic acid is shown to establish powerful stress resistance factors when plants face tough conditions. It also helps with osmoregulation (water usage), making the plant more resistant to stresses like drought, heat, cold, and other environmental stresses.

Lower Production Costs

OSA/28 is up to 63% cheaper than other silicic acid products. We pioneered new manufacturing techniques and sourced clean American-made ingredients to cut costs. We want to empower the grower. Soon as production levels make sense, we will find ways to lower costs even more.

Dosage and Instructions

  • Always mix OSA/28 in clean water before other nutrients
  • Allow to mix well to allow proper activation
  • OSA/28 is compatible with any feeding recipe
  • Your pH will drop after adding OSA/28 - add other ingredients and then adjust
  • pH of final solution depends on your medium (typical range 5.7-6.3)

  • Always mix OSA/28 in clean water before other nutrients
  • Compatible with other foliar applied chemicals and nutrients
  • Spray with lights off, just before day period
  • OSA/28 doesn't need a surfactant but is compatible depending on application method

  • For best results use OSA/28 every time you feed
  • Start using OSA/28 as early as possible during growth - All vegetative weeks and through week 5/6 of bloom
  • Double dose by root or foliar to reduce stretching in early bloom

Which bottle size is right for you?

Bottle Size Gallons Mixed Savings Pricing
4 oz (125ml) 250 G --- Get Pricing
8 oz (250ml) 500 G 18% Get Pricing
16 oz (500ml) 1,000 G 27% Get Pricing
32 oz (1 liter) 2,000 G 35% Get Pricing
1 gallon (4 liter) 8,000 G 41% Get Pricing
5 gallon (20 liter) 40,000 G 50% Get Pricing
Still need convincing? Request Sample

High Volume Grower?

If you are a licensed or large-scale cultivator, contact us for volume pricing.

Please send us an email or call (888) 656-4220 for a private consultation.

Retail Grow Store?

If you want to resell OSA/28 through your retail business, contact us for wholesale pricing and to setup a retailer account.

Please send us an email or call (888) 656-4220, ext 1 for sales.

Frequently Asked Questions

Why use OSA/28?

Silicon (as silicic acid) strengthens cell walls, increases nutrient uptake, and increases immune response. Other silicates are not bioavailable and take time+microbes to become available. This makes OSA/28 the fastest option for delivering silicon. Silicon also has a synergy with calcium. Many growers see increased calcium usage and response when feeding with OSA/28.



What is orthosilicic acid?

Silicon is the second most abundant element in the earth's crust. It is now known to be essential for optimal plant growth, health and production. Silicon in the soil isn't available (as various silicates). Plants can only absorb silicon as monosilicic acid (individual molecules). Orthosilicic acid is the stabilized form that transforms into monosilicic acid when mixed in water. Silicon chemistry is quite tricky so purity of ingredients and manufacturing excellence are necessary to get a stable and effective product to you.



Can't I make my own with something like AGSil16H for WAY cheaper?

This question is coming up a lot. This isn't an attack on AGSil16H--simply an explanation of the differences. There are several forum posts talking about how easy it is to make your own silicate product. You can but it won't be in plant available form, here's why...

So here's some good nerdy stuff my chemist team put together. Seriously nerdy. In summary, chemistry theory is often different than practical application. While much of what the IC thread says is accurate, it's not the entire picture. Hopefully this clears up a bit.

AgSil16H is pH basic. Silicate anions in AgSil16H are in polymer form (long chains)—unavailable to the plant. They could get very complicated depending on pH and the ratio of SiO2/M2O. When the pH of a liquid silicate drops below 10.7, fun things start to happen!

Liquid metal silicate will destabilize and become silica gel when the pH drops enough past the threshold! This silica gel is immobile and more or less permanent—it's what hardens the cell wall and gives the benefit we all want. This effect is awesome in the plant, but not in your nutrient reservoir!

Also, the solubility limit of amorphous silicic acid is around 100 ppm. Above this concentration, silicic acid undergoes autopolycondensation to form colloidal silica and eventually to silica gel. This condensation process is spontaneous and immediate. It also means that there is a limit to solubility in solution.

While dizziekush is correct in saying there is silicic acid formed at higher pH levels, there is an issue with silicic acid chemistry that he doesn't address. In weak acid or basic solutions, the silanol groups carry a negative charge, making them ionic and not passable through the cell membrane. Only in extreme acid solutions of <1 does silicic acid stay in the non-ionic monomer form—the bioavailable form everyone talks about.

This chemistry is tricky even to the chemists, which is why there is still open debate and research into the exact natural silicification process in natural soils.

In summary, AGSil16H is not just a “cheaper version of the same thing.” Nor is any other off-the-shelf potassium silicate or silica dioxide product. These compounds eventually will undergo transformation in proper conditions—like the acid environment created by certain microbial exudates. In longer term soil applications this potassium silicate can be effective. Much like crude oil versus gasoline, silicates must be “refined” before they can be used.

How does OSA/28 compare to other silicic acid products?

OSA/28 is manufactured by Ph.D chemists in the USA with domestically sourced ingredients. This means lower cost, fresher product, and more quality control. Silicic acid is tricky to make since it requires complex chemical reactions to produce a stable product. OSA/28 is shelf-stable and matches concentrations of other competitive products but at a lower price.



Isn't this the same as a cheap potassium silicate?

Not at all. OSA/28 is the difference between a person eating spinach or grass. They are both green leafy plants but humans can't digest grass without the help of cows! Potassium silicates (and other silicates) must be transformed into silicic acid before usable by plants. This process takes time and microbial-rich soil. Indoor growers demand speed and efficiency--both achieved with OSA/28.



Does OSA/28 stimulate SAR response?

Not directly that we know of. Many third-party studies show that silicic acid impacts various stress responses, especially with environmental factors.



How do I know if it contains silicic acid?

Many silicate products on the market claim silicic acid since it's a trending technology. The best indicator for a grower is the pH of the solution. Just drop a clean pH meter into a small amount of a silicon product (not directly in the bottle) and check the reading. If the pH is close to 7 or above, it is NOT silicic acid. Quality silicic acid products have a pH <1.



Does OSA/28 contain PGRs?

OSA/28 does not contain any plant growth regulators (PGRs), either natural or synthetic. Silicic acid, the main ingredient, is the only bioavailable form of silicon for plants. It is naturally found in healthy soils and is beneficial to all plants.



Where is OSA/28 made?

OSA/28 is the only true silicic acid fertilizer that is made completely in the USA with locally-sourced ingredients. We have a full-time team of chemists working in our facilities in Rhode Island. Our chemists have five Ph.D's and currently serve as professors at a respected New England University. By keeping research, testing and manufacturing in-house, we can maintain much higher quality standards than imported products.

OSA/28 is proudly made in the USA

Have another question?

Send us an email or hit us up on Instagram (@osa28silicon_) for quick and honest answers!

Laboratory Reports

We will always publish honest, third-party lab reports . . . even if it makes us look bad.

Plant Available Silicon

Compared to other national brands, OSA/28 contains the highest level of Plant Available Silicon. "Soluble Silicon" is the laboratory measurement of silicon in the form of monosilicic acid—the only plant available form. Higher concentration means more plant-strengthening silicon in every drop.

We knew OSA/28 was clean and strong but were curious where we stood next to other brands. So we analyze all brands on our dime to get past the BS hype and bragging that growers are sick of. Download the original lab reports below to see for for yourself.

To understand these numbers, you need to understand the testing procedure. Our laboratory partner, Thornton Labs in Tampa, developed the only nationally accepted test for Plant Available Silicon. Thornton developed the procedure in partnership with AAPFCO, the organization that decides acceptable fertilizer label claims. The procedure is highly involved, taking five days to complete, compared with single day silica/silicate mineral analysis.

This five day process mimics the same chemical mechanism plants use to absorb monosilicic acid—it is essentially a plant simulator! So while the resulting number is not the best indicator of how much silicon is in the bottle, it does tell us precisely how much silicon a plant is able to absorb from the product. There are no other recognized tests that gives this number.

*Based on third-party laboratory analysis by Thornton Labs. Competitor bottles were purchased from retail outlets within the last 30 days and shipped for analysis unopened. OSA/28 is not affiliated in any way with Mills Vitalize, Aptus FaSilitor, or PowerSi.



Download Lab Reports

Heavy Metals

Will be posted shortly...

How can we help you?

Best way to reach us for samples, ordering, or questions is to send us an email or DM on Instagram (@osa28silicon_) or call (888) 656-4220.

Power to the grower!