Water Based Exterior Polyurethane Clear Coat: Exterior 450 | General Finishes (2025)

All wood projects require preparation sanding. If you skip this critical step, your finish may fail.

Preparation for Raw Wood Projects
See our video: How to Prep Sand Raw Wood

1. 120-grit sandpaper followed by 150-grit or 220-grit sandpaper. Do not over-sand with fine-grit sandpapers; this will close and seal the wood grain, preventing ideal color absorption. Also, do NOT use steel wool on water-basedbased finishes; the particles will gettrapped in the finish and rust.
2. Remove dust with a vacuum, compressed air, an oil-free tack cloth or a water-dampened rag.
3. Let dry completely before applying GeneralFinishes Exterior 450.

New Stained Surface: Do not sand. Apply directly to stained surface.

Sealed Surface

1. Scuff clean with a non-woven abrasive pad & 50:50 mix of denatured alcohol & water.
2. Dry 1-2 hours
3. Sand lightly with 220-320 grit sanding sponge.
4. Remove dust.

CAUTION:Do NOT use Exterior 450 or any other clear coat, over white or light paints such as GF Milk Paint, or GF White Poly as it may cause yellowing. Any clear coatcan become reactive over wood substrates or existing finishes, causing tannin or dye bleed-though regardless of priming. All of GF's white paints are self sealing and do NOT require a topcoat.

NOTE: Exterior 450 White is designed to let the water permeate the finish; as it dries, the water releases back out to allow the finish to tighten down again. The UV additive in 450 Clear will protect the integrity of the finish, but will not prevent the wood from changing color from sunlight.

NOTE: Exterior 450 Whiteis not intended for decks. It can be used on tabletops that do not receive direct exposure to sun and rain. As with all furniture finishes, wipe up spills in a timely manner to protect the finish.

Join General Finishes University Facebook Group at https://www.facebook.com/groups/generalfinishesuniversity for customer support and learning opportunities for GF products. This group is a great resource for guidance regarding choosing the right product, mastering finishing techniques, troubleshooting, or sharing your finished projects.

General Finishes Exterior 450 WhiteApplication Steps

1. Work in a well-ventilated area.
2. Stir to reincorporate solids that have settled to the bottom of the can before and throughout the application process. Do not shake.
3. Test for adhesion when applying over an existing finish.
4. Thin as desired with distilled water; start with 5%, adding up to 10% by volume.
5. Increase open time, if needed, with 10-15%General Finishes Extenderif allowed by local regulations.GFExtender willimprove flow and leveling and increase open time, which is helpful in dry climates.California Residents:Adding more than 2% ofGF Extenderwill make the productsnon-compliant per SCAQMD Regulations. GF assumes no liability for the improper use of these products.
6. Apply 2-3 coats of Exterior 450. No more than three coats is recommended.More coats will not improve durability.
   • Hand application: Apply a liberal amount of product using a synthetic bristle brush, foam brush, pad applicator, or roller. Avoid pressure and excessive back-brushing. Brush along the wood grain using smooth, even strokes with light lap marks. Let lap marks dry; they WILL tighten down.
   • Spray application: Before spraying, strain topcoat through a fine-mesh filter. Spray wet films at 3-5-mil thickness. HVLP: 1.1mm-1.3mm spray tip, medium air cap.Verify tip sizes with your equipment supplier.See our spray tip size recommendations here.Keep your gun at a 90°angle, 6-8" from the surface. On large, flat areas, use wet, even patterns 6-8" wide. For narrow surfaces, reduce the fan pattern to 2-3" wide to reduce overspray.Overlap each pass 25%to conceal lines. Wear a full filter respirator (NIOSH/MSHA approved)and work in a ventilated space. Visit this FAQ for more information on spraying techniques.
7. Finish sand between coats with a 220-320 sanding sponge to improve smoothness and adhesion. Do not use steel wool.
8. Remove dust with a vacuum, compressed air, an oil-free tack cloth, or a water-dampened rag.
   WARNING: We do not recommend Exterior 450 White for exotic woods, ipe, teakor other dense, oily woods.

   Warning:Do not use water-based products with Linseed Oils or Danish Oils.

• Humidity is over 80%
• 3+ coats are applied
• Thick coats are applied
• To accelerate dry time in humid conditions, add General Finishes Accelerator and work in a space with good ventilation and air movement. If you decide to re-coat before the recommended time, test dryness.

Ready for exterior use: Allow to dry 5 days before exposingto the exterior elements.

Cure Time Before Use
Water-based finishes cure and harden for full use after 21 days in ideal conditions. Avoid placing heavy objects on surfaces that have not completely cured. Treat gently, and do not clean with commercial products during the curing period.

Application tools and materialscontaining water-based products can be cleanedwith soap and water or General Finishes immediately after use.

Product Spills

Spills may be able to be removed from fabric and carpet if cleaned immediately with soap and water.

Disposal

Discard unused product and waste in an environmentally safe manner; check with local fire and health regulation.

Life of Product

General Finishes products do not last forever, even when unopened. They are best used within 1 year. The life of the product may be extended with proper can closure and storage conditions. (see Storage Tips below).

Water-based products canlast 3-5 years ifthe can is unopened, in good conditionand stored in correct temperatures.

Product that is 3 years old will not look like product that is 6 months to 1 year old. You will see more stratificationorseparation as the product ages. Settling is natural. Always stirthoroughly before using.

FoulSmell

If your producthas a foul smell, itis contaminated andno longer in useablecondition.

Clumps & Settling

Gravity can cause some solids to settle on the bottom of the can and slight separation on the top. This is normal. If working with older productstir with apaint mixing attachment on a drill.

If the solids dissolve and clumps smooth out after mixing from the bottom, the product is in good condition for use.

Inability to reincorporate large, chunky lumps afterstirring for several minutesis an indication that the product has frozen and can no longer be used.

Storage Tips

See video tutorial: Tips on Storing Leftover Finishes
Water-based finishes crystalize and form a skindue to evaporation when the air-tight seal on a can is broken at first use. The following best practices will increase the life of your product:

1. Pry open sealed lids with a paint can opener by hooking under the lid's rolled edge. The use of a screwdriver can disfigure the rim and lid, impairing a complete seal.
2. Keep lid closed while working. Pour what you will use into a bowl, paper cup, or plate, and close can lid as you work.
3. Clean the chime of the canthoroughly with a paper towel before closing to create a completeseal. Product fallinginto the chime canbe minimized by using a pouring lid, such as Fitsall. Avoid wiping used brushes on the lid.
4. Pound the lid in placeusing a rubber mallet to avoid distorting the chime or lid. Dents in the lid from direct contact with a hammer can impair a complete seal. Alternatively, place a flat piece of wood over can lid and firmly pound shut.
5. Store in moderate temperatures.Avoid temperatures below 50°F/10°C or above 100°F/26°C. Keep from freezing. Frozen and heat-damaged product cannot be revitalized. Temperature-controlled spaces, such as a basement, are ideal for storage. Do not store product in an attic, garage, in direct sunlight, or next to something warm like a water heater or furnace.
6. Store can upside down to create a liquid seal, minimize evaporation and reduce the chance ofcrystallization.Decant remaining product from the can before stirring.
7. Decant leftovers to a smaller container when thefinish is almost used up. Alternative storage containers for water-based products are plastic FIFO bottles or glass bottles. Do not fill metal-lidded containers completely to prevent them from rusting.

The following water-based product mixturescan be stored:

1. Product thinned with up to 15% General Finishes Extender or General FinishesAccelerator can be stored, with the exception of thinnedGeneral Finishes Water Based Wood Stain.
2. Mixtures involving colors & sheens within the same product line, such as:
   • High Performance Satin + High Performance Gloss
   • Snow White Milk Paint + Coastal Blue Milk Paint
   • Amber Dye Stain + Merlot Dye Stain

The following product mixturesshould NOT be stored:

• Any water based product with thinned tap water; water often contains bacteria that will adversely affect stored paint.
• Topcoat + Stain or Paint
• Milk Paint + Chalk Style Paint
• Water Based Wood Stain + Dye Stain

• Remove dustwith a water-dampened cloth. Dust can build up over time and may scratch or dull finishes if not removed regularly.
• As with allfurniture finishes, avoid usingfurniture polish, cleaners or dusting sprays that contain silicone, alcohol, ammonia and anything acidic.Future finishes or touch-ups may not adhere properly or perform as desired over a contaminated surface.Some contaminants, such as silicone, seep through finish into the wood and often cannot be removed.
• Clean up water, alcohol and food spills in a timely manner and use placemats & coasters toprotect the finish.

Exterior 450 TopcoatWarnings and Warranties

• Flat:
  WARNING HARMFUL IF SWALLOWED. CAUSES RESPIRATORY TRACT, EYE AND SKIN IRRITATION.
  Keep out of the reach of children. Use only with adequate ventilation. Do not swallow. Do not get on skin or clothing. Avoid contact with eyes. Avoid breathing vapor or mist. Keep container tightly closed when not in use. Wash thoroughly after handling.
  
• Satin, Semi-Gloss, Gloss:
  WARNING CAUSES EYE IRRITATION. CAUSES SKIN IRRITATION.
  Keep out of the reach of children. Do not get on skin or clothing. Avoid contact with eyes. Keep container tightly closed when not in use. Wash thoroughly after handling.

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