Sunday, June 5, 2011

Crackle Enamel

My student Diana Pettiti studied for a number of years with an old-school group of enamelists in California before moving to Phoenix and she brought to the class some techniques I'd only read about and had never tried.  Diana was so great about sharing what she knew and letting me photograph the process.

So, what is crackle enamel?
Here is how I understand it (and please feel free to correct me if I get any of this wrong): the crackle effect is produced using a base coat of enamel with a very low co-efficient of expansion (which means it flows/ moves readily sooner than other enamels would at the same temperature) with a finely powdered liquid enamel on top.  Thompson Enamel makes a crackle base in clear, white and black.  Diana used the Liquid Form Enamels as the top layer (NOT the Liquid Form Brushable Enamels- I don't know what the difference is but they are separate in the Thompson catalog).

Diana is using Clear Crackle Base for her project

You need to prepare your metal as usual for enameling: metal should be grease free and free of scale if using copper and if you want to make sure your enamel stays clean. Do your counter side completely- if you know you are going to have 2 coats on the front, go ahead and do 2 coats of counter now.  Clean your front side then sift a nice even coat of the crackle base.  Depending on how thickly you sift, you may need a second application.  You don't want this layer to be super thin because you WANT it to MOVE.

Sifting the Crackle Base
Fired to maturity- The Crackle Base behaves just like any other
transparent enamel on copper so fire it normally

Next, you need to mix the liquid enamel in a small open mouthed container like a Dixie cup or condiment take-out type cup.  You mix with distilled water, no Klyr-Fire, around the consistency of tempera paint.  The enamel should coat the mixing utensil in a thin opaque layer.  You don't want it too watery or too thick. If it's too thick it may not split.

Buy Liquid Form Enamels in powder form so you can control the water content

Mixing the enamel- stir with a solid object to reduce bubles

Your metal with the crackle base should be prepped and ready to go before you start mixing the liquid enamel so once the liquid enamel is ready, pick up the crackle base piece and hold it from the underside.  You are going to pour the liquid form over the piece to coat the surface completely and you will need to be holding it so you can tilt it around to facilitate the coating process. Shake off any excess.

The piece has been coated and now Diana is letting any excess drip back into the container.
You can reuse the material if it dries out. Just add water and re-constitute.

Once the piece is coated, set it on a trivet to dry, which will take quite a while because the entire top surface is saturated with water.  You can place the piece on top of a hot kiln to speed things up or use a heat gun from underneath to dry the enamel quickly without reaching firing temp. I'm impatient so I like to do this a lot. Once you are absolutely sure all the water has evaporated, you can fire.

The kiln needs to be hotter than normal- ~1600F

You are going to fire in a HOT kiln.  For this process to work, the crackle base has to really move. You normally fire for about the same amount of time but really it just depends on when you see the cracking effect or not.  This is a somewhat capricious technique and if the base layer isn't thick enough and the top layer not the right consistency, the kiln isn't hot enough, etc. it may not work.  It will take some trial and error to really be able to get reliable results.  But oh, what results!

Right out of the kiln and look at the glow on the metal

As with most reds, the liquid form enamel comes out of the kiln looking black

Starting to "color up" as I like to say

The Liquid Form Enamels are opaques so what you see is what you get with their colors.  They can also be mixed to make new colors and used in painting techniques where they produce a water-color like effect.  One thing Diana did learn in my class is that if the crackle effect isn't as dramatic as you like, you can stick it back in the kiln and sometimes get a little more out of it.  If it doesn't work at all, then 1 of the 3 aspects (kiln heat/ time, crackle base ratio, liquid enamel ratio) is off and if it's definitely not the kiln, then it's one of the other 2 and you just have to start over.

I do need to add the sample size used in this demo was a 2 inch domed disc. Diana says the crackle also needs gravity and area to help it move so the effects may be reduced on smaller or flat pieces. I tend to work on smaller, flatter pieces and I find that adding a little more water to the top layer mix helps in achieving a crackle effect when base coat thickness, piece size and gravity aren't there to help you.


  1. I have been searching on the internet for a detailed description of this technique. Thank you for your wonderful pictures. I look forward to trying this. I'll keep you posted. Chicago, IL

  2. Thank you! Best of luck and let me know how it goes, especially if you discover something crucial I could add here to help others with this technique. :-)

  3. hello! is it possible for the crackle to happen when using a flux enamel for a base coat? i've been doing that with no result!

  4. Hi! You might be able to use another enamel that has a flow rate close to the crackle base coats (clear, white and black) made by Thompson but it will be a matter of experimentation. If you don't already have the Thompson work book, I recommend it because they have a chart in it of all the properties of their glass so you can compare those numbers. You will get the best results using a crackle base and making sure your top coat isn't too thick. I've had it not work when the top color layer is too sludgy when it goes on. I see more forgiveness in achieving a crackle effect when working on larger pieces, having a couple of base layers on (to promote more movement) and keeping that top layer from getting too thick. I normally work on flatter jewelry scale pieces so I don't want a super thick base and there's not much room for movement so I adjust the color layer to be thinner than perhaps it would be normally and I can still get a crackle effect to happen. Really shake the excess off after you pour the top layer on. Make sure it doesn't set up too thick. Hope that helps!

  5. Hi! Can you please tell me which liquid enamel you are using,by which name can I find them on Thompsonenamel. Thank you

  6. Hi Jelena,
    Here's the link for the top layer crackle colors. They also list the appropriate base coat enamels in "related products." Hope that helps!