Polycrylic, on the other hand, leaves a clear, non-yellowing surface, so it won't change the appearance of lighter woods such as maple or birch, or anything painted white.
I just grabbed a spray bottle and did a 1 part white vinegar to 10 part water mixture. While the polycrylic was just a little tacky (mostly dry) I sprayed it lightly with the mixture and wiped it down with a clean clothe. It took the yellow right off and it has never returned.
One of the drawbacks of polycrylic is that it has a loose, runny consistency that can be difficult to apply to vertical surfaces. It dries quickly, making it a great choice for small woodworking projects.
CAUTION: Do NOT use any water-based clear coat over bright whites such as GF Snow White Milk Paint, or GF White Poly as it may cause yellowing. Lighter-colored paints may alter slightly with a topcoat application, but the color shift is less noticeable.
So, a Class A sealer has the least likely chance of yellowing because Class A sealers conforming to C1315 are required to have the least yellowing characteristics however both types and all classes can and will yellow in most cases over time if not properly formulated - beyond the performance requirements of C1315.
Polycrylic, on the other hand, leaves a clear, non-yellowing surface, so it won't change the appearance of lighter woods such as maple or birch, or anything painted white.
CAB-acrylic lacquer is non-yellowing but it is best sprayed. Brush-on lacquers, which are mostly nitrocellulose, will yellow with age.
Emtech® EM9300 is an interior/exterior-grade waterborne polycarbonate urethane that resists marring and scratching, repels water and chemicals, and blocks UV light for an ultra-clear, non-yellowing finish that lasts.
Oil-based polyurethane ranks highest in terms of VOCs, whereas polycrylic is lowest. Water-based polyurethane stands between the two. If air quality is a major concern for you, or you have a poorly ventilated space, polycrylic is the option you might want to strongly consider.
Applying oil-based paints over a polycrylic finish is a terrible idea and not recommended. Polycrylic is a flexible sealant that contracts and expands as temperatures rise and fall. Oil-based paints, on the other hand, aren't as flexible and will crack and peel as the sealant underneath expands and contracts.
Three coats are recommended. After final coat, allow 3 hours before light handling and 24 hours before normal use.
Polycrylic is water based, but polyurethane can have an oil or a water base. There are both water-based and oil-based varieties of polyurethane from which to choose, but polycrylic sealers are strictly water-based.
(IF a second coat is desired, let dry at least 2 hours, then sand with very fine sandpaper (220 grit) to ensure an even finish and proper adhesion of additional coats).
Apparently, UV rays breaking down the finish is what causes it to yellow. However, improper application of the polyurethane can add to the yellowing or make it happen faster.
Minwax Polycrylic Protective Finish
A: Yes, but if you want it to have that flat, milky finish chalk paint is known for, then you shouldn't. This finish will give it a shine, even though it's satin. The recommended finish for chalk paint is wax.
The cloudy spots are likely caused by moisture trapped in the polycrylic, which can happen with water-based finishes, especially in humid conditions. To fix it, try lightly sanding the affected areas with fine-grit sandpaper (#320 or higher) and wiping the surface clean.
Polycrylic is less likely to turn yellow over time compared to oil-based polyurethane. This makes it a better option for light-colored woods and painted surfaces where maintaining the original color is important.
Water-based polyurethane has a tendency to interact more with the wood grain, which often necessitates the application of multiple coats to achieve a smooth finish.
Put a liberal amount of Water Based Wipe-On Poly on a clean, soft, lint-free cloth and rub into the wood. Allow to dry at least 2-3 hours.
One option is to use an emulsified oil in a natural color. Look for a lightly white emulsified oil, like Prato-Verde's Brio Zero oil, that preserves the whiteness of the wood while protecting it from yellowing. These oils contain white pigments that offer UV protection.
You can use an alkyd resin/soya oil varnish which will not yellow when applied in very thin in-the-wood type coats. Some alkyd resin/soya oil varnishes: Cabot 8000 series, Pratt and Lambert #38 or Sherwin Williams Classic Fast Dry oil varnish (at SW paint stores not the big box stores).
Wetsanding or polishing in stages with decreasing abrasives is the only way to get rid of yellowing clear as you are grinding down the discoloured material.
Most finishes exacerbate the problem leaving wood which ages to a "cigarette yellow" tone. The best way to create a pale bleached effect is to treat with a thin coat of diluted White Wood Dye after sanding. Once dry seal in with Finney s Trade Acrylic Varnish which enhances the bleached look of the stain.
Thompson's Water Seal
This is why in most woodworking blogs, their water seal always tops the list of recommended wood sealers. Aside from resisting most types of mold and mildew, it's also long-lasting. So you won't have to worry about reapplying a sealer every couple of years.
Where possible, choose a top quality water-based paint and/or a non-yellowing varnish, we recommend Dulux Aquanamel®. Acrylic paints do not tend to yellow as much as solvent-based paints, and are the only sure way to protect against premature yellowing.