How to Seal Your Paintings for a Glass-Smooth Finish

Once you’ve finished a painting, it can be difficult to wait to seal it! There’s nothing quite so satisfying as seeing the shine and luster of a painting restored with each swipe of sealant.

Attaining a glass-smooth finish is the dream, but making this a reality can be challenging. Depending on the type of sealant you use, you might notice streaks or uneven surfaces in your finished piece—issues that can be difficult to fix. There are ways to avoid these imperfections, and today we’ll talk about a few.

Supplies I Used

painting

Cure Time

If you’re not a naturally patient person, it might feel downright miserable to wait for your painting to cure, but rest assured it is worth it!

Allowing your painting to cure for at least 30 days will guarantee that your whole painting is completely dry. If you choose to seal your painting earlier than 30 days after it’s been poured, you might end up with a streaky, unevenly covered finished product—no matter how dry it looks.

Application: Sprays

Using a spray sealant is typically seen as the easiest option, but as with every method, there are a few tricks to getting it just right!

If you are unfamiliar with using a spray can, stop. Yes, spray cans are pretty easy to use, but when you’re spraying clear instead of spraying with a color, it can be difficult to see whether you are fully covering your painting.

If you don’t have a lot of experience with spray cans, consider buying an inexpensive can so that you can get comfortable with how an aerosol product works. Practice makes perfect, and in no time you’ll have a spray technique down!

When you’re ready to apply the spray sealant, do a test spray to see what the width and strength of the spray is. Then, make sweeping, side to side passes over your piece. Be sure to seal your painting on a surface that is safe to paint on since you’ll want to over spray the painting; meaning, your side to side passes should overlap the edge of the painting. If you stop at the edge of the piece, you will likely have a spotty finish around the edges.

Make sure you’re in a properly ventilated room and not directly inhaling the spray sealant!

painting 2

Application: Liquids

One popular sealant is Minwax Polycrylic. Safe for use over acrylic paints, this water-based sealer comes in a few different finishes: matte, satin, semi-gloss, and gloss. A few coats of this sealer, and your painting takes on a whole new life!

When I first began painting, I struggled with Polycrylic because it seemed like no matter how careful I was, there were always stroke marks left in the painting once the sealant had cured. This was so frustrating!

The thick consistency of Polycrylic and other similar sealants means that using a brush can leave very visible marks, which is not typically the desired look. Don’t give up on these thick, liquid sealants yet, though—there is hope!

The first method I’ve used to apply Polycrylic without the dreaded stroke marks is with a foam “brush”. These foam implements come in a variety of different sizes and shapes, and I’ve found that they work great when applying the product.

When using a foam brush, I like to pour a small puddle of Polycrylic in a corner of my painting and work the liquid outwards with light, even-pressured strokes. When I say light, I mean very light. The foam brush barely touches the surface of the liquid, and I never break the surface of the sealant.

A word of caution with foam brushes: Although they are a great way to apply Polycrylic or similar thick, viscous liquid sealants, make sure that you rinse and thoroughly dry the brush in between applications. If you allow the brush to harden between coats, you will not get an even surface and this will cause streaks.

I recommend rinsing the foam brush in warm water directly after you finish your application, and gently squeezing the excess water out of the foam with a paper towel. Then, lay the brush across the mouth of a wide cup so that air can circulate through the foam and dry it in the two-hour wait you’ll have in between coats of Polycrylic.

painting 3

Another method for application is the pouring method. We are all very familiar with pouring and manipulating on our pieces! I personally love this method and have had very good luck with the results.

Just be sure that if you are going to use this method, you use enough liquid! If you don’t, your liquid will not evenly cover your piece and you’ll be left with a bumpy, uneven finish. In this case, using a bit more than needed is a better idea than trying to add more later to even things out.

A few tips for this method: First, I have found that it’s best to wait about two-and-a-half hours between coats if you choose to pour on the sealant. I have followed the standard two-hour wait time that the Polycrylic website details, but I have found that the overall cure of the piece is much longer and the painting stays tacky for an extended period of time.

Because pouring the sealant on automatically means that the coat of liquid is thicker, an increased wait between coats is really crucial to maintaining the integrity of the final product.

Second, I would not recommend this method if you aren’t ready to waste a bit of sealant! Sincerely, this is one of the least efficient ways to seal your painting, even if the finish is very smooth and glassy. Be prepared to purchase sealant more frequently if this is the way you choose to go.

I don’t recommend using a paintbrush to apply Polycrylic or any other viscous sealant!

I emphasize this because I learned the hard way that paintbrushes leave marks…subtle, unwanted marks. As a matter of fact, I learned this when I sealed my largest piece, which was not the ideal time to realize a paintbrush was not the way to go!

I realize that some have success with this method, so if you do decide to take the paintbrush route, I strongly recommend investing in a good quality brush that will not shed while you are applying your sealant. Having to dig out an errant fiber is very little fun and will cost you some frantic time trying to even out the spot.

Seal of Approval

Sealing your piece is a wonderful way to brighten it, give it some shine, and provide durability for years to come. Make sure that you’re striving for an even finish so that your piece is represented in the best way possible!

TAGS:
SaraWagnerHeadshot

Sara Wagner is an author and artist from Upstate New York. She is the owner of Studio Blackwater and can typically be found covered in paint, cats, or her two young daughters. You can find her on Facebook and Instagram as @studioblackwater.

Comments

    1. That’s a great idea, Susanna! You can always repurpose pours that you’re not satisfied with.

  1. I used the pour method over a piece and it ambered horribly…. had to chuck a yummy piece😢, foam brush or super soft man made brush for me!😃

    1. Glad you found the brushes that work for you, Marie! This art form definitely requires a lot of trial-and-error but it becomes part of the pouring excitement.

  2. Thanks for your suggestions. Am wondering about using a silicone brush. Any advice or comments would really be appreciated.

  3. I found that the Minwax Polycrylic yellowed rather quickly. Within a month ruining my pours that had white negative space. I found that the sealants in the art section where the art paints are sold is the way to go. They don’t turn yellow.

    1. That’s awful that you had that experience! I’ve had nothing but good results with Polycrylic-perhaps it was just a bad batch that you got. I personally won’t use anything else.

    1. Yes, just make sure to gently wash the surface of the painting first with a damp cloth or powder. Some people rub cornstarch on the piece and then brush it away and that also seems to help!

  4. I tried the pouring method of the polycrylic on a few paintings recently and ended up with a lot of cracking. Do you have any suggestions of why that is happening and what I should be doing differently. I am hesitant to seal any others until I figure out why it was doing that. Thanks for the tips!!

    1. I haven’t experienced cracking with Polycrylic-it could be that it was too thick,or that your paint wasn’t quite cured yet. If you used silicone in your paint and if it wasn’t completely cleaned, that might also cause cracking.

    2. Yeah. I am thinking it was too thick. The paints should have been cured. I poured them over a month ago. I am going to try doing several much thinner coats and hope I have better luck. Thanks for the tips!

Leave a Reply

Your email address will not be published. Required fields are marked *