We’ve tried them both, and here is all the info you need to know about the two competitors:
OPI’s Black Shatter is still nearly impossible to get. It’s the first one of it’s kind to hit the market and it’s been extremely popular. (See Glambo post: “Black Shatter, Where are you?”) China Glaze’s crackle -in color! - was just released this week. If you polish your nails with either of these products, people will stop you to look. It’s a very cool effect and is definitely a conversation starter.
One thing we noted is that the OPI version grabs more heavily onto glitter polishes and gives more black coverage. To us, it seemed like more of a leather look than the leopard style spots the ad photos show. My first reaction after putting it over the light and pretty “Teenage Dream” was, “I didn’t want a Goth look.” But the more I looked at it, the more I liked it. The glitter sparkles through in the sun and I just couldn’t stop looking at my nails! Polishes with less glitter allow the Black Shatter to separate more, changing the effect and letting more of the base color show through.
We were curious about the China Glaze version because their polishes tend to be thinner than OPI’s. The China Glaze colors are very appealing as you can see in the video below. They come with packaged with a black nail polish and top coat. The colors crackle over the black base to give the effect.
The China Glaze black base polish was thinner, and I did one set of nails with one coat and one with two. The colored China Glaze Crackle polish went over the black, and it looked great. The Crackle glaze was thinner, which we liked. Using only one coat of black base didn’t seem to make much of a difference, so if you are in a hurry, you can skip that second coat. We like the idea of crackle colors over other colored nail polish. Our advice is that if you want a Black Shatter look, then use the black crackle or shatter over your favorite color - vs. painting your nails black first like China Glaze suggests. Both the OPI Black Shatter and China Glaze Crackle are a matte finish, so a top coat is essential for sheen and longevity.
We wondered, “How will they hold up?” I followed through by taking on the biggest opponent to any manicure: I spent a few hours filing paperwork. My nail polish did eventually chip, and it came off in large, thick chunks along the crackle lines. However, due to the nature of the imperfect shatter look, I was able to put just a little more Black Shatter on the tips, and follow up with another clear coat. It looked great again.
A few other things we noted:
The China Glaze colors appeared to be separating in our brand new bottles. Glambo suggests that you roll the bottle to mix it up well before polishing. Also, make sure that you wipe the top of the bottle after polishing and before you replace the lid. The shatter/crackle effect is drying and it makes the polish build up on the bottle edges. This will lead to a tough time twisting the bottle open later if the bottle isn’t cleaned properly.
We also like that the OPI version has a crackle lid, and the China Glaze clearly says, ‘crackle’ on the bottle. (I could just see myself grabbing a bottle from my polish stash a few months from now, not realizing that it was a crackle effect until it was too late.)
As of today, OPI’s Black Shatter is difficult to find. (Beware of E-Bay sellers that have ‘estimated’ shipment dates as they do not even have the product in stock.) The China Glaze colors are in demand, but seemed a little easier for us to get than the OPI version.
There are subtle differences, and we loved them both! The result: OPI’s Katy Perry Black Shatter and China Glaze’s Crackle each get Glambo’s Kiss of Approval.
The nasty RUST RING left in the shower by most shave cream containers. 
