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Friday, October 31, 2014

Sealant Testing on Metal -- The First of the Hardcore Experiments

The Sealant Experiments
by Laura Bracken

[Straight off the bat I want to thank those who are providing additional information and suggestions for my testing.  These first two rounds of testing were not definitive in any way and there's still lots of tweaking and more options to try.  

Please note that I did not "heat cure" the ProtectaClear.  I followed the manufacturer's directions.

In order to cover as many bases as I can, I will "heat cure" the ProtectaClear during the next phase of testing as many metal clay users swear by this.

It has also been recommended to heat the metal prior to soaking in mineral oil for greater efficacy.

In the next round, I will also be testing sheet metal along side the metal clay, for comparison.

Thank you all again for your suggestions and support!]

While some of my jewelry is more intricate and would be worn on special or infrequent occasions, a good portion of my designs are daily-wear pieces.  I am very (VERY!) concerned that the daily-wear pieces (in particular) can stand up to daily wear.

I make jewelry from fine and sterling silver, 14k gold-fill, traditional bronze and bronze metal clay, traditional copper and copper metal clay, and traditional steel and steel metal clay.

Steel, in particular, intrigues me, even moreso after taking a welding class at my local college.

However, the steel I use, whether it be sheet or powderized, is not stainless steel and the iron contained therein is subject to rust, leading to corrosion.  So one of my goals is to find ways to reduce the risk of rust showing up in my jewelry.

Additionally, there are times I'd like to protect my silver, copper, and bronze pieces from further oxidation.

So my goals for the sealant testing are to see:

  • What the sealant looks like on the piece (does it make the piece shiny, tacky, dull, etc?)
  • How well does the sealant resist water/air (to avoid rust and/or oxidation  
  • How durable is the sealant (will it last a long time?)
  • How easy is long-term maintenance of the sealant

Since powderized metalurgy (metal clay) produces a more porous end result, I opt for this material for my initial tests.

All of my tests used the same five identical charms.  Between testing I resanded (240 sanding band), cleaned the black and grooves with a radial disk, and repolished (220 sandpaper then 400 sandpaper), cleaned with denatured alcohol and allowed to dry completely.

Backing is Hadar’s Clay Low Shrinkage Steel XT, 6 cards thick, 24mm circle,  
Top is comprised of overlay of three Hadar high, one-phase firing clays
·         Center: White Satin (a steel alloy)
·         Right: Friendly Copper
·         Left : Dark Champagne Bronze

After firing per instruction the manuals, I sanded and polished to 400 grit.  I left the backing unpolished (but I did use a radial disk brush) because sanding and polishing metal clay burnishes the metal making it less porous and not all pieces are polished so I need to know the effect of sealants on unpolished pieces too.

For the liquid sealants, I dipped the entire charm into the solvent.  If I end up liking this sealant, I will try brushing on as sometimes dipping is less than optimal.

For the aerosol sealants, I coated according to the directions on the cans (generally three passes of the spray, 6-8 inches away constituted one coating)

Test #1  

I added a patina to the copper because I often patina my copper metal clay pieces and I need to know how the sealants work/react in real world applications.

One coating of each of the following:
Charm 1 (Protectaclear, dipped)
Charm 2 (Nikolas spray)
Charm 3 (PYM2 spray)
Charm 4 (Sculpt Nouveau Clear Guard, spray)
Charm 5 (W&N, spray)

All photos in this blog will get larger if you click on them (for those who like to see the details).
So here are the photos, before and after (right after… no stress testing yet).

I waited 24 hours for the coatings to cure. 

My first impressions of the finishes were:
Charm 1 (too glossy)
Charm 2 (fine)
Charm 3 (fine)
Charm 4 (fine)
Charm 5 (a bit too matt… lost some of the metal’s natural gloss)

Then I attached the charms to a sterling silver chain and wore the bracelet non-stop for two weeks.

In the above photo, the Windsor & Newton coating almost looks okay but that’s because it was the first one to wear off so at this point, I don’t think it even has any sealant left on it.

My conclusion is that one coating of these products isn’t enough protection.

I'm sure these products work great if a person:
A) doesn't wear the piece day-in and day-out
B) doesn't wear the piece in water
C) possibly stores the piece in a ziploc bag when not in use (this may be unnecessary for pieces with sealant).

But I prefer to know my jewelry can withstand normal wear and tear. I'd rather not sell high-maintenance jewelry at this point.  So more testing.

Test #2

This time I tripled the protection… if liquid, I dipped the charm into the liquid, let it cure/dry completely and repeated that two more times for a total of three coatings… if spray, I made three sweeps of the aerosol, let it cure/dry completely and repeated that two more times for a total of three coatings.

I switched up some of my sealants this time.  I may revisit this test with the three aerosol sealants from test #1 that I didn’t test this time (PYMII, Nikolas, Winsor & Newton)

Test 2 sealants:
Charm 1 (Protectaclear liquid)
Charm 2 (Mop n Glo liquid)
Charm 3 (Clear Guard spray)
Charm 4 (mineral oil soak, 4 hours)
Charm 5 (Renaissance Wax)

The coatings looked fine, I guess.  I think I’m acquiescing to the idea of coating my metal jewelry (something I’m not fond of) so I’m getting more and more used to the slightly glossy finishes of the sealants.

After allowing the sealants to cure for 24 hours, I put the bracelet into my tumbler with stainless steel shot, distilled water, and two drops of original Dawn. 

After fifteen minutes of tumbling, I noticed no effect so I put the bracelet back in and ran it for another 45 minutes (for a total of one hour).

I was trying to see which coatings would wear out first so was really surprised to see that although all the coatings look fine and intact, I was seeing rust on some of the pieces.  The first three charms all showed signs of rust.  Protectaclear the most, the other two slightly.  The oil soak and the Ren wax charms showed no signs of rust. 

None of the pieces showed signs of wear from the tumbling.  If the sealant wasn’t flaking off, does that mean some of these products allow water/moisture to pass through into the metal?

So those first three products may be fine for sealing copper and bronze from oxidation, but aren’t good enough for sealing steel against moisture. 

But now I needed to test things differently.

Test #3

Since the “tumbling in water” test kind of hit two subjects at once (water resistance AND wear and tear), I decided to break my sealant testing into smaller compartments. 

First, I want to see which coatings seal against water/moisture. 

After that, I want to see which coatings resist flaking for daily-wear type jewelry.

So the water resistance testing began.

I resanded the pieces and re-applied the same coatings as the previous test:
Charm 1 (Protectaclear liquid)
Charm 2 (Mop n Glo liquid)
Charm 3 (Clear Guard spray)
Charm 4 (mineral oil soak, 4 hours)
Charm 5 (Renaissance Wax)

After a day of curing, I put the charm bracelet into a dish of water and let the charms soak for four hours.


Charm 1 (Protectaclear liquid): front looks fine; some areas of rust on the back
Charm 2 (Mop n Glo liquid): for the most part, the front looks fine (the very bottom of the front has some discoloration, but in fairness to the product, when I dip a charm I continue to wipe at the bottom of the charm because of drip build-up, so it’s possible I compromised the results); same thing on the back… there is a little rust directly at the bottom of the charm where I’d been wiping after the charm was dunked into the sealant.

Charm 3 (Clear Guard spray): rust on the front in the recesses between clay types (this makes sense because my sweeping spray motions probably didn’t provide sealant to those recesses); rust also on the back (no recesses there).

Charm 4 (mineral oil soak, 4 hours): absolutely beautiful, no rust on either side and the recesses look good as does the overall evenness of the metal  on the front of the charm.

Charm 5 (Renaissance Wax): no rust on either side, but the recesses look a little funky where the wax got in and wasn’t wiped away.  Also, I think the finish looks duller on this one than on the oil-soaked charm.

Test #3b  

Although ProtectaClear, Mop n Glo, and Clear Guard all failed the water resistance testing, at a later date I can re-test them for how well they seal bronze and copper from oxidation (meaning those products may work fine on pieces that don’t contain steel).

But first I replace those failed three sealants with three other sealants and perform the water-soaking test.

As before I resanded (240 sanding band), cleaned the back and grooves with a radial disk, repolished the top surface (220 sandpaper then 400 sandpaper), cleaned with denatured alcohol and allowed to dry completely.

So now the line-up reads:
Charm 1 (Deft Clear Wood Finish Satin Brushing Lacquer liquid)
Charm 2 (MinWax Fast-Drying Polyurethane Clear Gloss liquid)
Charm 3 (Triangle Crafts’ Sophisticated Finishes Primer and Clear Sealer liquid)
Charm 4 (mineral oil)
Charm 5 (Renaissance Wax)

The Deft and Triangle Crafts liquids dried within a day, but the MinWax was still tacky after 48 hours so I kind of gave up on that one.  Even if it worked great… I’m not taking two weeks to coat each piece of jewelry. 

Both the Deft and the Triangle Crafts piece had three coats of sealant… two coats brushed, and the final coat dipped.

When placed into the water bowl for soaking, the Triangle Crafts piece got a milky coating on it. 

After hours of soaking then taken out to air dry, neither piece showed signs of rust (or so I thought… keep reading).  Five days later, still no signs of rust.

By that time, the polyurethane piece was dry, and although it only had one coat I decided to go ahead and water test it while I was there anyway.

No rust.

Now if you look at the close up photos, you’ll see a tiny bit of rust on the Triangle Crafts piece.  That makes sense seeing as how the sealant appeared to dissolve when the charm was put into the bowl of water.



It seems to me, sealants on metal may serve different purposes for different artists and/or for different projects.

I want a sealant that:

  • Keeps rust at bay or any metals containing iron
  • Maintains current patina on copper and bronze
  • Does not flake/wear off easily
  • Is easy to re-apply by customer if necessary
  • Ideally, would keep the super polished shine of bronze

I also want to explore what differences exist for polished metal versus unpolished, porous metal.

As I said, I still need to test these sealants for these other factors, but here’s my chart of how they stand up so far.

3 sealant coats
Rust Protection
Preserve Patina
No Flaking
Customer Maintenance
Mineral oil soak (3+ hrs)


Renaissance wax

Somewhat easy

Deft Clear Wood Finish Satin Brushing Lacquer liquid


MinWax Fast-Drying Polyurethane Clear Gloss liquid*


Triangle Crafts’ Sophisticated Finishes Primer and Clear Sealer liquid


Mop n Glo liquid
Sub par

Somewhat easy

Sculpt Nouveau  Clear Guard aerosol
Sub par

Special handling but easy

ProtectaClear liquid


Winsor & Newton matt varnish aerosol

Special handling but easy

PYMII aerosol

Special handling but easy

Nikolas aerosol

Special handling but easy

 * Only one coat of polyurethane

I will let you know when I update this chart.

All this rust talk being said, however, I'd like to mention a curious thing (although probably not as curious as I first thought).

Let's back up and talk about silver.  I noticed many years ago that when I "wear" a piece of sterling silver jewelry, I have to polish it a lot less often than if I leave it sitting on an open-air shelf in my bedroom.  Meaning, wearing a piece of sterling silver seems to slow down the oxidation of the metal.

This could in part be that through hand-washing and daily showers, the piece is actually getting washed regularly, but I think it also has to do with the metal being in contact with body oils.

My own purposeful "wearing" tests on steel and bronze have yielded odd and at times surprising results.

For example, I have two steel rings that I wear.  These are similar to these.

I don't take them off when I wash my hands, and I even go against the advice I give my customers which is to towel dry any steel jewelry immediately rather than letting it air dry.

Neither of these rings shows any sign of rust.  

I could almost expect that on the inside of the ring where my body oils would be in contact with and therefore distribute onto the metal.  But how does the outside of the ring stay rust free?

The only feeble theory I have at the moment is that these rings are not polished, so being very porous metal (as metal clay is), the oils from my hands distribute throughout the entire metal piece, acting as protection.

I suppose one way to test this theory is to polish up a ring and see how it stands up to the same abuse.

BTW, I will be adding testing with gun blue when I next update this chart.

Regarding bronze, the other day I wore a necklace and a pair of earrings made Friendly Bronze.  I ended up walking for five miles carrying a backpack and two bags.  It was 95 degrees out and I was one sweaty SOB for about four hours.

These bronze pieces had been polished to the brightest golden shine exactly like these pieces.

I was super surprised when I arrived at my destination, took off the jewelry, and saw the state it was in.

That's why I added another item to my list of things I'd like to see if it's possible... preserving the super shiny surface of highly-polished bronze in a practical setting (meaning wearing it not just leaving it on a shelf forever).

I did have another piece that had been polished then oxidized over time and easily polished back up with a Sunshine cloth.  So I'm wondering if the difference was the salt content (my sweat) that made such a devastating dull look to the polished bronze.  Which, btw, did not polish right back up easily with a Sunshine cloth.

Stay tuned for more info always.  :-)


  1. I always learn something from reading your blog. I hadn't even heard of steel metal clay.

    What great testing! I tend to use Ren Wax a lot so I am glad that it comes out well in testing.

  2. Laura, are you sure you weren't a famous scientist in another life? What a thoughtful testing plan! And what an enormous amount of time for planning and execution - very impressive. Great due diligence!!! You're a super blogger:)

  3. Thank you very much for this excellent post! I'm not a big fan of P** Clear and (worn) steel objects rust so fast with me it's terrible.
    When you say "mineral oil", what is it? like Paraffine?

  4. Great post! Just to add to the rust prevention part, what I do is first heat the steel and dip it hot into mineral oils. This was recommended to me by a professional blacksmith here. It's supposed to help better penetrate the oils. Then I soak a bit and wipe the excess. Once dry, I then clean with alcohol on a soft cloth. Let dry (dehydrator) and then I dip in Protectaclear, dry and second coat it. So I use both ouls and sealant. I've been doing this for about over 2-3 years and it seems to really work well over time and use. Also, always recommend to clients to put on perfume *before* their jewelry, otherwise it can alter the sealant on base metals, but it's also not good on precious metals. Looking forward to you future tests! Cheers!

  5. Wow! Thanks so much for your time and energy posting this for us! I am just finishing up my Hadar Accreditation and have been revisiting my sealing options. You have saved me a lot of time and money!

  6. Hi Laura, you did a great job on this and thanks for sharing it! I use the same method as Angela Crispin, but instead of using Protectaclear I use Renaissance Wax which dries very quickly and is very easy to use.

  7. Very helpful. I had never heard of the mineral oil soak, so I'll investigate that. But what I was wondering with the Protectaclear is that they say not to expose it to water until it's fully cured which you can speed up by heating the piece in an oven at 180 degrees F for 2 hours, or I think wait 5 days after application to expose the piece to water. I was wondering if the Protectaclear was fully cured before you did your water tests. But I see this is an old post, so I'll probably have to run my own tests. I'm not crazy about the whole sealant thing either so looking for the best alternative.

    1. Hi Roberta and thanks for commenting on my blog post. I'm always glad to find a fellow researcher/experimenter.

      I'm willing to give Protectaclear another shot. I did wait the five days, but I didn't put on three coats. I'm still undecided how I feel about plastic/varnished coatings on metal. And I'm still not sure about the long-term use of sealants (do they peel, chip, scratch?).

      I hope you share results of any tests you do also.

  8. Re; my previous comment. I just now noticed that you didn't heat the Protectaclear pieces, but did you wait the 5 days or whatever the cure time is before you did the water test? Thanks!