A well-engineered, water based polyurethane will be equal in clarity to oil-based polyurethane. The main difference is usually color: water based polyurethanes are completely clear and (again, if well engineered) will not yellow over time. This is ideal if you want the natural color of your wood to remain constant.
The Short Answer: All polyurethane will yellow over time. While modern technology has extended the amount of time it takes to yellow and reduced the extent it can yellow by, ALL polyurethane (including polyacrylics) will yellow.
The easiest option is to apply a clear, water-based finish such as Minwax's Polycrylic.
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.
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.
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.
Polycarbonate (PC)
Polycarbonate is a hard plastic known for its durability and resistance to yellowing. Unlike silicone or TPU, polycarbonate holds up better against UV light, oils, and heat.
Unlike linseed oil-based polyurethanes, our URETHANE formula will not yellow over time. Excellent water resistance.
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).
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.
Yellowing of clearcoats is a natural phenomenon during weathering processes, as well as from extreme baking conditions, due to polymer degradation. However, occasionally yellowing may be caused by unexpected chemical reactions occurring in the clearcoat.
In summary, polyurethane offers superior durability and protection, making it the better choice for high-use and outdoor applications. Lacquer provides a beautiful, glossy finish and is easier to repair, making it suitable for indoor furniture with lighter use.
High clarity protective coating for indoor wood projects provides a crystal clear finish. Premium polyurethane retains the same clear finish as the day it was applied and will not yellow with time. Dries to touch in 2 hours.
There is no difference between the terms urethane and polyurethane. That might seem confusing, so here's a quick explanation. Polyurethane is a polymer. A polymer consists of repeating units that are chemically linked in a particular pattern.
One alternative to polyurethane sealants is silicone sealants. These sealants are made from silicone, a synthetic rubber. Silicone sealants provide a flexible bond that can withstand extreme temperatures and weathering. They also have good resistance to chemicals and UV light.
Waterlox is Safer and More Durable. Customer reviews and industry experts provide ample evidence supporting Waterlox as a safer and more durable option for specific applications, such as in horse barns.
Pure tung oil will not continue to yellow over time, it does not support mold/mildew growth, and it will not become rancid. Pure Tung Oil will also fully cure, meaning that it lasts longer than most other pure oil finishes and is essentially permanent.
While TPU offers excellent shockproof and scratch-resistant qualities, it is more susceptible to yellowing when exposed to sunlight due to its absorbent nature. On the other hand, PC material is colorless, odorless, and boasts a stable molecular structure, making it resistant to yellowing.
The Benks Lucent Pro phone transparent case is designed specifically to address the issue of yellowing. Crafted with advanced materials that include UV stabilizers, this transparent iPhone case offers a lasting clarity that other cases simply cannot match.
Which clear iPhone case doesn't turn yellow? The two cases we've tested that are the most resilient to yellowing over time are Apple's Clear Case and Speck's Presidio Perfect-Clear. At the end of the day, we prefer Apple's Clear Case for its minimal design compared to the Speck Presidio Perfect-Clear.
The Best Interior Water-Based Polyurethane Finish Option
ZAR® Interior Water Base Poly Crystal Clear is a clear protective coat recommended for light bare wood or light stain colors. It is environmentally safe and non-yellowing, so you can use it with confidence to protect your interior wood projects.
If you're short on time, here's a quick overview: Composition: Polycrylic is water-based, while polyurethane can be oil-based or water-based. Application: Polycrylic applies in thin coats and dries quickly; polyurethane takes longer to dry.
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.