Choosing a Curing Compound Sprayer

The sprayer decides how even your film is, and an uneven film shows. Most of what you need to know about the sprayer is already printed on the compound’s data sheet: the tip flow, the pressure and how to mix. Start there, then pick equipment that matches it.

What kind of sprayer do you use for curing compound?

A pump-up concrete sprayer handles most slabs, driveways and walls. Data sheets name the same two classes. The W.R. Meadows 1100 data sheet says “hand or power sprayer, such as a Chapin 1949,” and the Euclid KUREZ DR VOX sheet allows a pump-up sprayer or an airless industrial sprayer.

Spray beats rolling. The Dayton Superior J11WD sheet allows a low pressure sprayer, roller or brush, but says spray is “the preferred method.” For the full job, from mixing to the second coat, see how to apply curing compound.

What tip and pressure should you run?

Run a flat fan tip sized to the rate your compound’s sheet gives. W.R. Meadows prints the same spec on several sheets, including the CC-309-1WS data sheet: “a spray tip that produces a flow of 0.5 GPM (1.9 LPM) under 40 psi (.276 MPa) of pressure.”

Other makers size it differently. The MAPEI Mapecure DR data sheet calls for “a low-pressure, airless industrial sprayer with a fan tip (rated at 1 U.S. gal. [3.79 L] per minute),” or a 3/8 in. (10 mm) nap roller. On walls, Dayton says to use two light coats and “a fine spray tip.”

The tip only sets how fast it comes out. Your walking pace sets the rate on the slab. Work out the gallons first with the curing compound coverage calculator, then check the gallons used against the area when you finish.

What specs matter on a pump-up concrete sprayer?

Look for seals rated for the chemical, a flat fan tip, a pressure range that reaches the data sheet psi, a solids rating that covers your product and a wide opening you can clean. Two makers publish these specs for their concrete sprayers. This is not a ranking; it shows what to read on any spec sheet.

Check the solids rating against your product’s data sheet, especially for higher-solids cure and seals. Solo says its 1 gpm flat fan is fitted “for spraying higher solid content curing compounds.”

When do you need a power sprayer instead?

On paving, and on any job with a spec that calls for one. The FHWA curing guidelines note that the AASHTO guide specification calls for “fully atomized spray equipment with a tank agitator and wind guard.”

The agitator matters most with white pigmented compound. The Iowa DOT spec says to agitate the compound before it leaves the container and “continuously during application.” A pump-up tank has no agitator, so on a large white pour either shake the tank often or move to a sprayer that has one.

How do you keep it from clogging and dripping?

Stir the compound, keep the tank clean, and never mix products. Most clogs come from settled solids or dried compound in the tip and wand. The 1100 sheet warns about “clogged or partially clogged spray tips,” and says not to let the nozzle drip on fresh concrete.

• Stir first, gently. The 1600-WHITE data sheet asks for gentle agitation and says, “TO AVOID FOAMING, DO NOT MIX EXCESSIVELY.”
• Do not thin. J11WD says, “Do not thin. Do not use high speed mixing equipment.”
• Do not mix carriers. CC-309-1WS says mixing with a solvent compound causes separation. See water-based curing compound for why.
• Start clean. CC-309-1WS says equipment “must be clean and free of any previously used materials.”
• Stop drips at the wand. Chapin sells a dripless shut-off whose seals at the tip “eliminate buildup and drips when the shut-off is disengaged.”

How do you clean a curing compound sprayer?

Clean it the same day, before the compound dries in the hose and tip. CC-309-1WS says water-based compound cleans up with soap and water before it dries, but needs mineral spirits once it has dried. KUREZ DR VOX says to clean tools with warm, soapy water before it dries.

1. Depressurize the tank and pour leftover compound back into its pail.
2. Rinse the tank, then spray clean water (or the cleaner the sheet names) through the wand until it runs clear.
3. Take the tip off and clean it separately.
4. Store the sprayer empty. Chapin says not to store chemicals in the sprayer and warns that different chemicals can cross-contaminate even after cleaning.

If the sprayer left stripes or drip marks on the slab

Expect the marks to stay. The 1100 sheet says drips and uneven patterns put down more film, which “may cause the cement to hydrate at different rates,” and that removal of the film “will not change the spray patterns mirrored in the concrete surface.”

What you can still do:

• Fix the cause before the next pour. Replace a worn or partly clogged tip, add a dripless shut-off, and test the pattern on cardboard first.
• Do not spot-spray dark areas. More compound adds to the uneven film.
• Check what goes on next. If the slab is getting tile or a coating, heavy streaks may need extra removal work; see curing compound and flooring before the flooring crew arrives.

Keep the tip spec and rate for your product on the curing cheat sheet in the truck.