Paint and finish are necessary and widely used across the world, especially in the wood industry. A lot of guidelines exist about the proper application of wood finish, such as polyurethane. But, very little is written about what to use to remove a wrongly applied or existing urethane coat from wooden surfaces. The same is true for varnish or epoxy, although there are lots of resources on paint removal.
However, we’ve studied the less focused topic, in addition to others. Research shows that conventional sanding is good, but using a best-quality stripper like CitriStrip Stripping Gel or Dumond Smart Strip makes the removal more convenient, regardless of whether the coatings are polyurethane, varnish, epoxy or paint.
Types and Basics of Stripper
A stripper is a chemical designed simply to remove coatings and finishes while cleaning the underlying wood surface to prepare it for reapplication.
Already coated surfaces cannot be refinished or repainted directly, as the new layers would not adhere to that surface properly. It is essential to remove the existing layers before a poly or varnish recoating and strippers come to your rescue there. It is easy and less tiresome than the other mechanical removal process such as sanding or scrapping.
Strippers fall into three main categories – caustic, solvents, and biochemical.
Caustic strippers: water-based solutions available in two forms – potassium hydroxide and sodium hydroxide. The caustic lye reacts with the finish and turns it into soap, loosening and removing it from the surface. Caustic strippers may burn the skin and irritate the lung.
Solvent strippers: cause bubbling to the coats by softening or dissolving the bond within the finish substrate and film, leading to easier removal. Alcohol, acetone, ketone, toluene are some solvents, while the most common one is methylene chloride. When we call solvent strippers, we generally understand methylene chloride-based solvents. They are really great but pose significant health risks, including capacity failure of blood to carry oxygen, kidney or liver damage, or even cancer. You may even create a combination of alcohol, toluene, and methanol for a cocktail stripper.
Biochemical strippers: are plant-derived solvents, for example, terpenes from pine, dimethyl sulfoxide from wood pulp, lactic acids from corn sugars, and citric acids from citrus. They contain biochemical ingredients capable of breaking the bond between finish substrates to loosen and remove. In addition to those ingredients, biochemical strippers contain NMP, a super reacting yet safe agent. By combining forces, these strippers will give you the desired stripping – but they need to be kept on the surface for a relatively longer time than other strippers. They may irritate your skin slightly but are generally safer to use than the rest.
What Type of Stripper is Best on Wood?
Caustic strippers give super stripping on any wood coating, with a removal specialty on alkyds. But they darken the wood, requiring another bleaching step to neutralize. This step is mostly harmful to wood, though. Moreover, they don’t work on temperatures below 50-degree Fahrenheit.
Solvent strippers, especially the methylene chloride, offer a little advantage over other strippers in removing epoxy and polyurethane finishes from wood. They give relatively quick results too. But, due to the severe health risks associated with these, we do not recommend them often unless you have the ability to take enough protective measures. They require high ventilation, which makes it tough to apply in cold weather.
What else is left? The Biochemical strippers! Yes, that is what we recommend to use for removing coatings, whether it’s painted on baseboards or sealant and finish on furniture. Best paint strippers will chew through most combinations of alkyd and latex paints without darkening or causing damage to wooden surfaces. Although they take longer to react and remove the finish, they are the safest among available options. Additionally, you won’t spend much on them. That’s why it’s what experts recommend. All the products listed above are biochemical strippers.
Get Best Strippers – Remove Polyurethane, Varnish, Paint, Epoxy
Polyurethane is relatively new and has a broader application. It acts as a finish, while some of those can seal or paint. In contrast, the varnish is not sophisticated like polyurethane, but it has various applications too. However, epoxy resin is quite sophisticated and creates a strong adhesion to wood when used as a sealant or finish. Paint is completely different than all of these. But, they still have similarities on several grounds, such as objective and removal methods. The product you use for stripping polyurethane can also be used for removing paint, varnish or epoxy.
But not all strippers or liquid sanders are good at removing all types of coatings from wood. What stripper is best depends on the surface and coatings to be removed. Considering possible issues, like we always do, we’ve made a shortlist of top-quality multifunctional strippers:
Best Overall – Citristrip Stripping Gel
Runner Up – Sunnyside Multi-Strip
Best Spray Stripper – Citristrip Aerosol
Best for Small Projects – MAX Strip Stripper
Safest Option – Safe ‘n Easy Citrus Gel Stripper
Heavy Duty for Oil & Lead Based Coatings – Dumond Peel Away
Just a notification, whatever you want – best polyurethane remover, best varnish remover, best paint remover, best epoxy remover or other wood finish remover – these multifunctional strippers are good enough to meet your demand and serve the purpose.
Methods of Removal
When removing paint or wood finish like polyurethane or varnish, there are two key ways to go about it – mechanical method (sanding or scraping) or chemical method (stripping).
Sanding – sandpaper sanding requires less technical knowledge, but it ensures an excellent finish – smooth and no residue. However, you may have to spend a lot of time doing this – it may even take a few days of sanding for larger projects. Although a highly effective process, therefore, it is labor-intensive.
Scraping – is close to sanding, where the paint or finish is removed by scraping or abrading using scraper tools. A tool with a flat steel blade head mounted on a wooden, plastic or metal handle, generally used to remove paint, occasionally wood finishes, from surfaces, is called a scraper. This takes less time and labor, but it is unlikely that you’ll get a smooth finish as sanding ensures. Therefore, scraping should be supported by a secondary sanding process.
Stripping – is the final one, where you’ve to use strippers, a chemical designed to remove coatings while cleaning the underlying wood surface to prepare for reapplication. Everything just opposite to sanding and scraping makes paint strippers a much better choice for removing paint and wood finish. But you’ll require a dulled-edge scraping tool to scrub the softened coatings after applying strippers in some cases, or you can use sandpaper too. Use of pressure is rarely seen for third-stage rinsing. It’s faster and less labor-intensive. Although applying this involves better understanding and technical knowledge, it is still the easiest method for getting hardened paint, polyurethane, and other wood finishes off.
Others – a few other ways are still there that you may apply to remove paint, polyurethane and varnish. Although they won’t probably be as effective as the top three explained above, they still exist because of specific dedicated applications. Anyway, amongst those include the use of heat guns and pressure washers.
Safety Application – Tips and Tricks
How to apply strippers is discussed in another blog. However, for maximum safety and effective use of chemical coating remover, you should follow certain practices:
- Avoid harmful chemicals like methylene chloride and use products that have fewer threats to the body and environment.
- Cover the floor and furniture with a chemical-resistant tarp.
- Polyurethane and paint removers should be used either in a well-ventilated indoor area or directly outdoors. You should bring the particular furniture or wood object outdoors before applying removers, if possible. If not possible, ensure a fan circulates the air outside from inside.
- Avoid direct bodily contact with the stripper and wear protective clothing and use the right tools & equipment when applying, even outside the house.
- Apply based on the instructions given on the label. Brush with short strokes in the grain direction and maintain the suggested thickness. Aerosol spray-can handles small projects, while paint spray gun is excellent for stripping massive projects.
- Keep the applied removing agent on the wood surface for the recommended time given on the label.
- Use a scraper with relatively dulled edges to remove the softened coating to lift it in the grain direction and a rotary motion.
- Some removers may require a neutralizing agent to reduce the pH level. Usually such strippers recommend the neutralizing solution in their packages. Test if the pH level gets down to 7 after neutralizing.
- If the coating still refuses to come out, you may require to apply a high PSI pressure washer for surface rinsing.
- Dispose of the waste stripper as said below.
Water or Oil Poly/Paint – Effectiveness of Stripper
Strippers contain ingredients that can simultaneously soften and remove oil-based and water-based paints or polys. While water paints and finishes are dissolvable in water, oil paints or polys are not. So, what you can use for oil finish also applies to water finish, but not vice-versa. However, for water-based varnish and polys, regular strippers are enough, while you may consider adding paint or urethane thinner to strippers when applying it on oil paints or finishes.
Can Strippers Get Dried Paint or Polyurethane Out of Clothes?
Strippers lift and remove any paint or finish that it comes in contact with – on wood, metal, or cloth. Surely, you can get dried paint or polyurethane out of cloth using strippers. It does no harm to the wood or metal when removing coats, but it’s a little tricky to guarantee fabric.
Although there is no evidence so far that strippers discolor the fabric or spoil its quality. But, since this is not the result of extensive research, it is difficult to predict what reaction will occur in different fabrics. Therefore, when using any paint or finish removal agent, you should wear appropriate protective clothing and avoid wearing something precious.
Dispose of Paint Strippers
Strong recommendations are not to pour the paint strippers or likely wood finish removers into the soil or down the sink to dispose of it. The safest way to dispose of is to put strippers in a household or local hazardous waste collection program. The rules for such programs may differ by state or country.
Vinegar – Use on Paint, Polyurethane and Varnish
Vinegar is a natural alternative to strippers, but it is by no means as effective as strippers due to the absence of other chemical ingredients. Although you can use vinegar to soften paints, polyurethane or varnish coatings, it will take a long time to bear fruit. Also, you have to put much effort, as an extra scraper application to remove the softened coating in the next step will be necessary. If the coating is too thick, like 10 layers, it is unlikely to get the expected result.
But yes, it’s an excellent cleaner for a wood finish covered in dirt or has lost its luster – natural and nontoxic. Neither will it damage nor will it wrap the finish on wood surfaces. Therefore, we suggest you use this for cleaning wood finish, not removing coatings.
Chemical strippers are made in such a way that they are effective for removing almost all types of paints, polyurethanes, varnishes and epoxies. But some of them may have more ability in some specific works. We’ve listed products with the ability to remove any paint, urethane, or varnish from the wood in all directions. In this case, you can undoubtedly rely on the above-selected strippers.