Mixed Media Fine Arts

Preserve your Burn - How to Clear Coat Metal Sculptures

Weeks of hard studio work welding, grinding and applying patinas have finally paid off - your new piece is pure genius. However, the metal requires a protective topcoat in order to impede oxidation and corrosion. Even if the piece has been left to weather naturally the weathering will eventually need to be arrested. Just encapsulating corrosion won't stop it from progressing. Without protection the moisture and chemicals in the air will alter the color of the patina and eventually turn the piece into a pile of rust in the corner.

 

The application of a clear coat is the final step of the patination process (see BURN post: Burn-Junkie Color Lounge: An Introduction to Chemical Patination). Deciding what kind of topcoat to use depends on 1- the patination 2- the metal and 3- the look you want to achieve: matte, satin or gloss. The flatness or glossiness of the sculpture is related to how light reflects or diffuses off the object’s surface. Like everything else, figuring out your preference requires some experimentation. It’s an aesthetic call.

A nonporous lacquer or a wax or metal oil clear coat is critical for sculpture preservation. A clear coat wil impede corrosion, protect the patina and improve the sculpture’s overall resistance to scratching, flaking and other surface damage. When working with metal it might seems like a savvy economical decision to reach for the RustOleum but I don’t recommend using cheap spray coatings. Yes, they are inexpensive and easy to use – pop the top, point and shoot; but, in time the finish can flake and, without adequate UV inhibitors, the patina can take on a garish yellow hue. It will break your heart!

It is soul crushing to watch your sculpture develop fish eyes, orange peel or take on some other streaked, bubbled or bruised horror, especially if you have taken care to follow a product’s instructions. The thing is there are learning curves associated with the successful application of the various finishes. In this post, I’ll tell you about my favorite topcoats and the (extra) steps I follow when using these products.

 

Waxes and Oils

Waxes and oils have been used as surface protectants for 2000 years. They produce a lovely dull finish that can be buffed to a rich natural luster that will enhance the natural patination of metal and the details of the fabrication. Waxes and oils look like the metal itself, only better. Waxes and oils do not actually bind with the metal – they are coatings on top of the metal - so they must be reapplied periodically (every year or two depending on the storage conditions). A clear lacquer applied over the surface will reduce this problem and will preclude the need for reapplication of the wax or oil.

There are a range of oils and waxes that may be applied to metal. Oils include linseed oil, lemon oil, walnut oil, Penetrol, and metal oils created especially for metal work. Oils made especially for metal have hardener added and are made with or without pigmented color (www.SculptNouveau.com). This line of oils is beautiful and easy to use (see below). But there are a couple of tips. To begin with, oils should be applied sparingly as yellowing may occur. Use thin coats and let the oil harden and dry completely before buffing. This can take a couple of days, which is longer than noted in the instructions. When you buff, be sure the cloth you use is lint free! Also, make sure your cat hasn’t been sleeping on the cloth. Picking out fur from a still tacky finish is not fun.

Johnson’s Wax, Constantine Wax, Carnauba, Treewax™, and Renaissance Wax are some of the waxes that can be used with metal. A mixture of bees wax, turpentine, and linseed oil may also be used. Finally, Sculpt Nouveau manufactures a great range of waxes especially for metal work with added pigment, UV inhabitants and hardeners.  When you apply waxes, do so in thin coats as they will be smoother and easier to buff. Also note that waxes may darken the patina’s color over time.

The application of waxes and oils is pretty much the same. Clean your piece of dust and grime. Ensure the sculpture is completely dry before the application of the finish. If moisture gets trapped beneath the finish it will cause problems. I use a heat gun to warm up the piece first. That way I know the piece is dry and a warm application provides a smoother process. It also helps with penetration of the finish. Warm the piece gently, to about 200°, and apply a thin coat of the wax or oil with a brush. Allow the piece to cure at least 12 hours. Once dry and hard, burnish the piece with a soft, clean cloth. A second and third coat may be applied as desired. When warm application is not possible the wax or oil may be applied cold. Wax that is applied cold can be diluted with benzene, naphtha or mineral spirits to make application easier and smoother

 

Non-wax Sealers

Urethane, lacquer or acrylic can be used over hot and cold patinas as well as over sculptures that have metal or oil coatings. All sealers should be applied in thin coats and given plenty of time to dry between coats. There are a lot of lacquers to choose from and they all have learning curves.

The two clear coat finishes I use most frequently are: DiamondFinish and Permalac. DiamondFinish produces a high gloss finish while the Permalac finish is a more natural satin. Both are very durable and neither will yellow or flake over time, even with exposure to sunlight. These are my go-to clear coats but both can vex you to violence.  The unique issues of each product can easily ruin your finish or at least ruin your day. Hopefully becoming acquainted with the issues will allow you to take precautions that will make the product a better finish and you a better person.

 

KBS Diamond Finish

KBS Diamond Finish is a clear coat that can be applied directly to prepped ferrous and non-ferrous metal surfaces. The product can also be used over patinas, paint, coatings and on non-metal surfaces. It is self-leveling and will not leave brush marks. Once cured, the high-gloss finish is very durable and resistant to surface damage. Diamond Finish clear coat can be applied by brush, roller and conventional spray gun and does not require the addition of a hardener.

You know how sticky a two-part epoxy can be right? This stuff has that same sticky viscosity so unless you want to take a Xylene bath, put on latex gloves before you get started. Also put on a mask and turn on your exhaust. Now that you look great and are breathing easy, read all these suggestions thoroughly before you open the can. You’ll want to apply 2-3 thin coats and allow each coat to cure for at least six hours (I allow 8-12 hours between coats). The ideal temperature range for application is 60-75° F with low humidity. So, if your application is too thick or is applied in wet or humid conditions surface bubbling can result when released carbon dioxide becomes entrapped beneath the top surface layer of paint. The sensitivity to humidity has not been a problem for me but it can be so, if it is humid, use a heat gun to assist with the initial drying. That will take out some of the humidity. And, if the finish doesn’t flow on easily, thin it 10% with Xylene.

The big issue I’ve found with the Diamond Finish is that once the product is exposed to oxygen, it hardens quickly. The instructions include six warnings related to this: Do not paint out of the can; Keep lid on at all times; Do not shake can; Seal can immediately after use; Keep paint groove free of coating; After a good stir, dispense a working amount of Diamond Finish into a separate container and seal original can immediately; Unused paint should NEVER be put back into the can as it will shorten its shelf life and cause pressure build-up possibly popping the lid.

Let me just say, these warnings do not even begin to convey how urgent this issue is. You may think you know what quickly means but you need to go next level here. Further the instructions give the impression that you can address this issue easily if you keep the can clean and close the lid. Hysterical! They tell you to dispense into a different container and put plastic wrap between the lid and the can. None of these approaches work. If open the can, apply a thin base coat, close the can and go to bed – the rest of the can will be completely congealed into a hardened mass by the morning!

Diamond Finish is great but it is expensive. Learn from me. If you are going to use this product (and you should) this is how to approach it:  

  1. Buy the product in the small cans, only as much as you need for the job. Don’t think Costco here. Large is not better.
  2. Don’t even think about pouring the product into a glass jar with a screw lid. You’ll just end up with a paperweight.
  3. Lay out everything you’ll be using before you open the can: Gloves on. Exhaust on. Brush or sponge or sprayer ready to go. Xylene poured into a jar for cleanup. Cloth ready to clean up your brush and spills. Sculpture set in the place where application will occur.
  4. Open the can. Pour out only the amount you need into a container you can throw out once you complete the application. Cover this smaller container with some kind of lid immediately.
  5. Now, as quickly as you can, clean the lip, sides, and top of the can (use a paper towel damp with Xylene). Clean the can thoroughly and pour a little of the Xylene into the groove of the can where the lid will snap down.
  6. This next bit is essential - before closing the can of Diamond Coat, spray a long blast of Bloxygen into the can - then immediately snap the lid closed and make sure it is closed securely. Bloxygen is basically Argon in a spray can. Argon is heavier than oxygen so it keeps the moisture out of the can and prevents the Diamond Finish from hardening. Otherwise, during storage, the oxygen or moisture that's sealed in the container will continue to cure and thicken the Diamond Finishes and totally ruin the leftovers. I have used Argon from my MIG when I’ve run out of Bloxygen, but it is an inferior way to dispense Argon in this circumstance. I’ve also heard you can breathe into the can (since CO2 is heavier than oxygen) but since Argon from my MIG barely works, I find the notion pretty ridiculous. Don’t be cheap and skip this step. The cost of losing a can of Diamond Finish will be a greater loss.
  7. With the can of Diamond Coat securely closed up, take a deep (but quick) breath and return to the clear coat you’ve dispensed. Apply it to your sculpture. If it is thick you can add 10% Xylene – but you’ll really need to stir and stir this mixture or the xylene will likely take off your patina.
  8. When you’ve finished the application, throw away whatever is left along with whatever xylene is leftover (and get the smelly refuse out of your studio), clean your brush well (before the product dries in the bristles) and pour yourself a drink. You deserve it. I know this all sounds a little stressful but the finish IS worth it and once you get used to the process, it’s not so bad.
  9. A couple of final suggestions – Be very sure your patina is completely dry and cured before using Diamond Finish. I use different brushes for different colors when I am applying the first coat of Diamond Finish as I’ve had colors (especially reds) bleed into one another if I just brush in one continuous stroke with a single brush. This is not a problem after the first coat cures. Another thing I often do is to apply an initial quick coat of a finish like Sculpt Nouveau’s Smart Coat (a water based urethane/ resin based finish). Smart Coat application and clean up are fast and easy and the finish dries quickly, creating a barrier between the patina and the initial Diamond Finish so the colors do not bleed. Finally, take the time to try out your patina and finish on a scrap piece of metal before applying it to your sculpture. This way you’ll move through the Diamond Finish learning curve without ruining your artwork and becoming suicidal.

 

Permalac

I really love the final results of a Permalac topcoat – smooth, natural and durable; but I have experienced significant problems with the application. It’s really tricky. I don’t know why they don’t provide honest directions to troubleshoot issues but they don’t. The instructions read as if Permalac can be applied by any competent three-year-old; but it’s not true. Permalac can be maddening and since the instructions are lacking, panic is a natural response. Fortunately for you, I have ruined finishes, panicked, started over and ruined them again until I have finally figured this stuff out (famous last words).

Permalac is a clear solvent-based lacquer containing UV and corrosion inhibitors. The topcoat comes ready to brush or spray on, in matte or stain finishes. Permalac also comes in a spray can, which is a great convenience, but it is very expensive. For large projects the cost can be prohibitive. The liquid Permalac is a more economical choice. If you are using a sprayer, you must dilute the Permalac with a thinner. Be careful to use the smallest necessary amount and ensure it is well mixed; otherwise your patina may also be thinned during application. Your layers should be applied as thin as possible. Barely mist on the layers and allow 10-12 hours drying time, even though the directions tell you to apply a second coat in and hour or two.

Surface preparation is always important but you’ll need to pay extra close attention if you are going to use Permalac. Dust or grease (even ambient dust in the room and oils from your fingers when handling the piece) can result in the appearance of rough patches of the surface. While these can be addressed with light sanding, the result is never perfect and the final product may not make you happy. To minimize problems, be fastidious in cleaning your piece (using a lint-free cloth) and wear protective gloves throughout the application to prevent the transfer of oils from your hands. Clean your piece before the initial Permalac application and clean again before you apply additional coats.

The second issue with Permalac is sensitivity to moisture. This is a really big issue! The directions indicate that there may be problems in high humidity but high humidity is not defined and it appears to be any more than .005% humidity. So, assume moisture is going to be a problem. I address the moisture issue with heat (I use a heat gun) and acetone (I use acetone in a spray bottle that can emit a very light mist). After cleaning the piece, heat the surface with a heat gun to 200°. Don’t skimp here. Make sure your piece is dry and warm. Apply the Permalac in a very thin layer. Apply sparingly with a small brush or a sponge applicator. Don’t use a brush like one you’d paint the walls with. If you apply the Permalac too thickly, bubbles may form. If there is any moisture, bubbles may form. If you breathe or blink during application, bubbles may form. To combat the frequent bubbling, be ready with a heat gun and acetone spray. As soon as you apply Permalac, use the heat gun to assist with the drying. And again, don’t skimp here. Take the time the topcoat needs…or bubbles may form. If you see bubbles appear, gently mist the spot with acetone and blast it with the heat gun. Go light on the acetone. You don’t want to take off the patina beneath. Between the spray and the heat, you can beat the moisture isssue. After the application of the Permalac do not touch the piece for 10-12 hours (or longer). While the Permalac dries to the touch pretty fast it seems to need the extra time to totally cure or there will likely be moisture trapped between the layers. Keep an eye on your piece during the first hour of drying in case further drying assistance (heat gun/acetone) is needed. Apply at least three coats to your piece. After the final application, apply a thin layer of wax (your choice) on top of the Permalac coating and allow that to cure as well.

Instructions for using patinas, solvents, clear coats etc. are often lacking in the details that are necessary for success and to troubleshoot problems. I recommend a run through on scrap metal before you apply any topcoat. The easiest way to do this is to use a piece of scrap of the same metal as your art piece. As you apply your patina to your art piece, also apply it to the scrap. By taking the time to make a dummy piece for testing you will be able test out your patina and clear coat on something you don’t care about. When problems occur, you will be able to make adjustments as needed without a full-scale psychotic break.