Yes, you can, but it is not recommended. Varnishes are built-up layers of different chemicals that create a barrier between the paint and the air. Applying one coat of new varnish on top of an older layer may not adhere properly to the underlying surface.
Moreover, if you want a quality finish over your product, applying a new coat of varnish over the older one is not a good practice.
When used directly, there are chances that it can lead to peeling or flaking in a short period. So, it’s best to remove all existing coats and start fresh with your application process.
Can I Varnish Over Varnish Without Sanding?
I’m sure you’ve seen this question on the internet and have been wondering about it for a while. The answer is yes, but with some caveats.
The first condition to keep in mind is that if you’re using a high-quality varnish, there’s no need to sand off your old varnish before applying new coats of varnish. However, if you’re using cheaper or lower-quality products, it’s best to use light sanding to eliminate any dirt or imperfections that might be hiding under the old layers.
Moreover, one important thing to remember before applying a new coat over the old is to check how much of the old layer is remaining. If it is in excellent condition without any peeling layer and no deep scratches, you can just clean the older layer of varnish using soap and water.
After that, wipe it down using acetone and apply a very thin layer of primer on it, followed by one or two coats of concealer. Once it gets dry, apply three fine coats of good quality varnish over it in a well-ventilated area to save yourself from its off-gassing smell.
But, if the condition of the old layer is terrible and it has scratches and peeled-off portions, then the recommendation for you is to sand off your old varnish before applying a new coat.
Otherwise, the fresh coat will become more susceptible to water and alcohol damage. Also, be careful while sanding off the older layer of varnish, do it with precaution so that you don’t sand the original layer of wood.
Related Read: How To Apply Varnish With a Roller?
Do You Have To Sand Varnish Between Coats?
Sanding varnish between coats is something that many don’t think to be compulsory, but it surely can provide a better finish. However, you need to know a few essential things before jumping in and sanding your hard work away.
The most important thing to consider is the type of varnish you’re using and its need for optimum performance. For example, with some varnishes, the only time you would want to sand between coats is if they are still tacky when dry; this will allow them to adhere better.
On the other hand, acrylics do not require sanding since they can cloud up the finish. So always make sure you understand how your chosen varnish works before diving into any workshop tasks.
Moreover, it is not that sanding varnish between the coats will decrease the quality or lose the coat’s shine. Instead, it will only benefit you but will consume more time also. You can choose to sand off the varnish layers in between coats, but you need to do it properly with adequate knowledge of it.
You can sand varnish after the coat has dried; you should use fine sandpaper(220-240 grit) to sand the surface lightly. This will ensure that the surface has good adhesion before you apply the next layer.
Sanding also produces a white film over the finish but will disappear as you apply your next layer – do not worry about this because it is normal.
Remember not to use steel wool with any water-based topcoat because it might develop rust after the finishing coat is applied.
How To Apply Varnish Over Varnish Paint?
To get a clearer, smoother, and lustrous layer of varnish over paint, then do follow these steps:
1. Clean And Sand The Surface
If you want a smooth coat of varnish, then you need to have a clean and smooth surface. If the surface is oily or dirty, then you may not get a good finish after applying varnish over it. Try to wash it off using a soap solution and sponge, and leave it till it gets dry.
After this, your preparation should also include the sanding process of your painted surface. Use 100-grit sandpaper and sand it lightly to rough it up so that varnish adheres to it perfectly.
By any chance, if you see the paint is peeling off from any portion of the surface, you can use a wire brush to remove that loose particle and continue with sandpaper until you feel the surface has become smooth to touch.
Note that if you are not able to take the flaky or loose portion off with a wire brush, then don’t force it. Remove the paint if only it’s loose and coming off.
Related Read: Should You Paint Over Chalk Paint?
2. Add A Coat Of Primer
Varnish will not stick to oil-based paint without adding a layer of primer on it first. Older painted surfaces are usually oil-based. To find out if the paint applied on the surface is oil-based, test it by rubbing alcohol on a small surface area.
If the solution wipes off, it’s probably an oil-based paint, and you need to add a water-based primer before varnish. But if you can’t tell if your paint is water or oil-based, just add a primer anyway because painting over a water-based paint with a primer will not hurt anything.
3. Choose The Varnish Gloss
Pick your gloss carefully. The term “high-gloss varnish” means exactly what it says. It gives the painted woodwork a lustrous finish. Use it to provide a modern look for the product.
The shine of a medium-gloss varnish is enough to be captured by the eye but not enough to make it stand out. The low-gloss or satin finish varnish keeps the paint’s older look or gives it a more antique appearance.
4. Apply The Varnish
You can achieve a smooth finish if you’re skilled with a paintbrush, but the most outstanding results are usually achieved by spraying.
An aerosol can of water-based varnish is usually enough for most modest applications. Hold the can at a 30-degree angle about 8 inches from the surface. Start spraying it in an overlapping pattern to coat the surface lightly.
Some corners of a few items are challenging to clean, and you can’t reach it with sandpaper, use steel wool instead.
You can even use steel wool if the surface is carved or detailed. But, sand carefully to avoid sanding through the paint in those areas. If you want more gloss and protection, apply up to three extra coats of paint after sanding.
Do You Sand The Last Coat Of Varnish?
The majority of professionals believe that sanding off the last coat of varnish will harm you more than it will benefit you. You will make your project look cloudy and dusty if you sand the finishing coat. Therefore, it is advisable to sand between the coats only to make it adhere properly but not the last coat.
There is no need to sand it off or use a heavy-duty scraper because that would cause more damage than good. Generally, people ask to sand the last coat of varnish if any sand particle remains in the final coat.
Additionally, there are cases where the surface doesn’t feel smooth even after the final coat of varnish. To avoid this, proper sanding between the coats of varnish is essential.
Moreover, before applying the final coat, simply wet the surface and wipe it down using newspaper soaked in water until no debris is left.
Make sure to dry off any excess water before applying your topcoat, which will give you a beautiful finish without damaging what has already been done.
Can I Put Dark Varnish Over Light Varnish?
The clear answer to this question will be that you can put dark varnish over light varnish, but it is not advisable to do so because you may not get desired results.
To put dark varnish over light varnish, you will have to start a process of removing the light shade varnish from the surface. Usually, the layer of varnish gets harder with time, and the power of absorption and gummy properties gets weak.
So, if you try to apply dark varnish over that hard layer, then there are high chances that it will not stick to it. Even if it sticks in any case, there are chances that it will flake after a shorter time.
Additionally, even if you try to apply the darker varnish, the results might not be as shiny and appealing as expected. The varnish applied, especially on wood, gets absorbed by the wood, and VOCs of some varnishes cause a change in the color of varnish with time. This can hamper your efforts to apply darker vanish as it may cause a particolored finish, making the surface look duller.
However, if you want to make it work, you will have to sand off the earlier applied light varnish from the surface. Then you need to clean all the dirt from it and clean it properly so that no dust particles remain while applying the new dark varnish coat. Then apply three coats of varnish over the surface in a well-ventilated and dust-free area.
Also, you can try putting dark varnish over a lighter one, take a small piece of any surface on which you are planning to put dark varnish. Apply the procedure on it and check whether it can work in your case or not. If it gives you the expected result, then you already know how to do it on the entire surface.
Related Read: How To Paint Over Varnished Wood?
If you’ve ever been told to put varnish over a surface that already has previous layers of varnish on it, then I hope this is the first time you’ve heard about what not to do. Instructions given above will ensure your new layer of varnish goes on evenly, giving off an even shine for many years.