Calcium lignosulfonate has a long history as a water-based binder in foundries. It gives dry strength to sand cores and moulds, burns out during casting, and costs far less than most synthetic binders. This page explains how it works, where it fits, what to measure in a trial and the limits a foundry should check first.
- Role: temporary organic binder that hardens on drying.
- Typical uses: dried sand cores and moulds; additive to clay-bonded sand.
- Main benefits: water-based, low cost, burns out to help shakeout.
- Main checks: moisture pick-up of dried cores, gas evolution and sulfur.
How Calcium Lignosulfonate Works as a Foundry Sand Binder
The powder is dissolved in the mixing water or added as a liquid grade. When the sand is mixed, the solution wets each grain and forms thin bridges at the contact points. Drying removes the water and leaves a solid lignosulfonate film that holds the grains together. This gives the core or mould its handling and pouring strength.
When molten metal fills the mould, the binder near the metal decomposes. Losing the binder weakens the sand, which makes cores easier to knock out after casting. The same decomposition releases gas, so venting and permeability matter.
Where It Fits in the Foundry
| Use | How the binder is used | What to watch |
|---|---|---|
| Dried sand cores | Mixed with sand, rammed or blown, then dried or baked to develop strength | Dry strength; moisture pick-up in storage |
| Dried sand moulds | Mould faces or whole moulds bonded and dried before pouring | Surface hardness, gas evolution |
| Clay-bonded (green) sand | Minor additive alongside bentonite and water | Effect on moisture control and flowability |
| Mould and core coatings | Organic binder in some water-based refractory coatings | Coating adhesion and drying |
What to Measure in a Trial
| Property | Why it matters |
|---|---|
| Tensile or compressive strength after drying | Cores and moulds must survive handling and metal pressure |
| Strength after storage in humid air | Lignosulfonate films absorb moisture and can soften |
| Permeability and gas evolution | Gas from the binder must escape without causing defects |
| Retained strength after heating (collapsibility) | Low retained strength means easier shakeout |
| Casting surface and sulfur pick-up | Confirms the binder does not harm the metal |
- Fix the sand, its grain size and the drying conditions.
- Test a ladder of binder additions on a dry-solids basis against your current binder.
- Make standard test specimens and measure strength after drying and after humid storage.
- Pour trial castings and inspect surface finish, gas defects and shakeout.
- Choose the lowest addition that meets strength, then confirm on three production lots of binder.
Which Grade to Trial
| Grade One (GAC-CaLS-1) property | TDS value |
|---|---|
| Lignosulfonate content (dry basis) | 55% min |
| Water-insoluble matter | 1.5% max |
| Dry matter / moisture | 95% min / 5% max |
| Sugar / reducing sugar | 9–10% / about 7% |
| Total calcium and magnesium | 5–8% |
| Packaging | 20 or 25 kg lined woven bags; 500 or 600 kg FIBC |
Values are typical and from the current TDS (Rev. 2.0). Batch results are stated on the certificate of analysis.
Limits to Keep in Mind
- Humidity: dried cores can pick up moisture and lose strength. Store them dry and use them within a set time.
- Sulfur: the binder contains sulfur. Ductile iron and some steel castings need a metal check before use.
- Gas: organic binders release gas on pouring. Keep binder additions as low as strength allows and vent cores properly.
- Strength level: where high strength or fast cycle times are needed, resin binders are usually the better choice.
Foundry Sand Binder: FAQ
How does calcium lignosulfonate bind foundry sand?
Dissolved in the mixing water, it coats the sand grains. When the core or mould is dried, the film hardens and bonds the grains together. At casting temperature the organic binder burns out, which helps the sand break down at shakeout.
Is it a replacement for resin binders?
Not in general. Lignosulfonate is a water-based, low-cost binder that develops strength on drying. It is used on its own in some dried cores and moulds and as an additive with clay-bonded sand. Resin systems give higher strength and faster cure.
Why should I check sulfur?
Lignosulfonate contains sulfur, and some is released when the binder decomposes. Ductile iron foundries in particular control sulfur closely, so check the effect on the metal before adopting it.
Which grade should I trial?
Green Agrochem calcium lignosulfonate Grade One (GAC-CaLS-1), whose TDS lists foundry casting sand. It has 55% min lignosulfonate content on a dry basis and 1.5% max water-insoluble matter.
Grade, Documents and Samples
Specification, TDS and MSDS: calcium lignosulfonate (CAS 8061-52-7). Related reading: lignosulfonate in refractory castables and ramming mixes and calcium lignosulfonate uses and grades. For samples and a COA, use the contact page and tell us your sand system and casting alloy.
