Cast Iron with First Coat of Paint header

Painting Tips from the Antiquarian

You end up doing a lot of painting when you restore antiques.  Tips and tricks abound, but I thought it might be a good idea to share some basic concepts so my followers can jump start their painting.  I’m going to cover painting cast iron and sheet metal because this will comprise the vast majority of painting a restorer will do.

Cleaning

I buy most of my tools and other antiques in poor condition for the challenge of restoring them.  Like me, you will probably end up with your fair share of heavily rusted and outright dirty iron.  Sheet metal, hopefully not pitted, will be rusty and dirty as well.  After disassembling the item (like the Atwater Kent speaker), I set everything aside until I have enough pieces of metal to warrant a trip to the sandblaster.  A powered wire wheel works fine, but for most items, especially intricate ones, I prefer sandblasting with fine grit.

 

Cast Iron & Sheet Metal Ready to be Sandblasted

Cast Iron & Sheet Metal Ready to be Sandblasted

Protecting

Once the metal has been sandblasted, it will be completely bare and will need protecting quickly or it will rust.  In fact, any water that touches the bare metal will rust it before your eyes.  I usually start painting the day I pick up the freshly sandblasted metal.  My preferred “primer” is Flat Black Rustoleum “rattle can” spray paint.  This paint is usually cheaper than actual primer and other Rustoleum paint colors.  For priming, there is no particular order to painting.  Just pick a side and spray.  You can paint one side of the metal per day.  If it’s not humid and the paint dries quickly, you may get away with painting both sides.  Remember to spray paint outside on a day that is not windy.

 

Note in the above left picture that only one side has been painted.  The arrows show the bare metal that will be painted when the piece is dry and can be flipped over.  The above right picture shows the unpainted “underside” if you will of the speaker base.  The picture below shows the metal flipped and painted.  The metal now has one complete coat of paint.  Once dry, carefully inspect the piece to make sure there is no unpainted/exposed metal.  Cast iron typically has a number of pits that require additional coats of “primer” paint.

Second "Primer" Coat of Paint

Second “Primer” Coat of Paint

Filling Pits

The bulk of antique cast iron was sand cast meaning that a mold was created in moist sand and molten iron poured in.  Sandblasting removes dirt, rust, and any debris (such as sand from the original mold) that is on the surface of the metal.  Therefore, cast iron will have a number of pits in the surface that may need to be filled depending on the intended restoration.  Since these pits are merely cosmetic, I use spackle to fill them (several applications) prior to applying what will be my restoration paint coats.

 

The above left picture shows a “primed” flywheel with numerous pits that were exposed during sandblasting.  The above right picture shows two flywheels with pits that have been filled with spackle.  Once the spackle dries and has been smoothed, you can apply your first coat of paint.

Finish Painting

At this point, the order of painting is of great importance.  You will need to choose which side of the metal will not typically be seen (the back side) or the side that will not be the focal point because this will get painted first.  The order is back, front, back, front.  You need to apply at least two coats of paint on each side of the metal to get a good finish.  Again, I use Rustoleum can spray paint.  Do not apply a heavy coat of paint.  Strive for a gentle coat.  Sheet metal requires an extremely gentle coat to prevent runs.  If you paint too heavily (sheet metal or cast iron), you will have to scrape and sand paint runs before you can continue painting.  Less is more.  You can always apply more coats later.

Cast Iron with First Coat of Paint

Cast Iron with First Coat of Paint

The above picture shows an initial coat of gloss black.  Gloss dries slowly, so you will only be able to paint one side per day.  Let the piece dry inside overnight (preferably not inside your living space) to prevent debris and bugs from adhering to the fresh paint.  After several coats (back, front, back, front, etc.) you will need to apply the last coat of paint to the front of the piece.  Spend your time on this final paint coat.  This is the side that will show or be the focal point.  Paint evenly and, for larger pieces, don’t let any part of the surface dry before completing the entire face.  If part of it dries, the paint mist created while you are still painting will cause the gloss or satin surface to be a different sheen in the dried areas.  This will require an additional coat of paint the next day.  The picture below shows the final coat of paint applied to the face of the piece.

American Treadle Frame Being Painted (June 2012)

American Treadle Frame Being Painted (June 2012)

Hopefully this short tutorial will jumpstart your restoration projects.  Let me know if this helps and feel free to ask questions in the comments section below.

2 comments on “Painting Tips from the Antiquarian

  1. Rov

    You really should try hanging your projects on wire (eg cheap baling wire). Put some eye bolts or simple nails on the ceiling joists or on a 2 by angle frame outdoors, but spray painting is better without wind or direct sun. Warming the parts first to remove all moisture is a good idea also. I would use body filler, not spackle, which tends to chip out too easily.

    1. techwriter007

      These are all great ideas. I hung the legs of my computer table while finishing them. It’s documented here. I especially like your suggestion about the auto body filler. I have not used it on cast iron. Fortunately, I have only needed to fill small but deep holes in the cast iron.

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