How to fix a grout line in your mosaic art

Posted on November 29th, 2014 by admin in Mosaic Ideas


Have you ever watched the grout of your mosaic seemingly shrink before your eyes as it hardens?  Arrrrg!  The grout lines are no longer flush with the tesserae and tiny pinholes mysteriously appear.  Now what?

As the grout sets and hardens, you may notice grout shrinkage (i.e., the grout lines are like little valleys where the grout sinks and isn’t flush with the tesserae).  This used to happen to me a lot when I mixed the grout too runny.  However, since using thick, pasty grout, I’ve experienced much less grout shrinkage.  Don’t fret!  It’s an easy fix.  Simply re grout the mosaic.  It’s a lot easier the second time, especially when using thick, pasty grout.

If you’re not crazy about the idea of going through the whole grouting process again, here’s a little trick I use at the end of my normal grouting process.  After the last wiping cycle when the grout has set for about 45 minutes, go back and carefully inspect the entire mosaic for tiny pinholes, missed areas, depressed grout lines (i.e., where the grout is no longer flush with the tesserae), and other grout imperfections.

CAUTION: Cement (i.e., grout) is mildly caustic so don’t do this process with your bare hand.  Wear a glove for protection.

Use the leftover grout if it’s still workable.  If it’s not, then mix another small batch (two tablespoons of grout powder are usually enough).  Add just a bit of water at a time so you don’t end up with grout soup (i.e., the grout should be thick and pasty, not runny).  Wearing a glove, use your index finger to scoop up a dab of grout and rub it into the imperfect area.  Fill the little pinholes that invariably occur, and the little gaps that you missed, and the little depressions that seem to form as the grout sets.  Simply fill in those imperfections with your finger, wipe off the excess grout from your finger, and then use your clean finger or a dry paper towel to carefully wipe up the excess grout without disturbing the grout line.  Voila!  The imperfections are fixed.  Don’t accept those imperfections!  Go back and fill them in.

Do not use your bare hand to do this.  After a while, the skin will wear away and you’ll bleed all over your beautiful mosaic.  Yes, you will, indeed, bleed if you spread and wipe grout long enough with your bare finger.  It happened to me!  I could see the skin wearing away on the tip of my finger, but I was stubborn, thinking I’d be done soon.  A few wipes later, the last layer of skin was gone and it bled.  Now, I always wear a rubber glove to protect my skin.  I don’t use latex medical gloves because they’re relatively expensive (about $100 for a box of 50).  Instead, I use vinyl synthetic, powder-free exam gloves.  I can get a box of 100 at Walmart for about $30.  I only need one glove at a time because I only use my right hand when spreading and wiping the grout (i.e., I don’t need to glove my left hand).  That equates to about $0.30 per mosaic, which is well worth it to avoid the pain of wearing your skin down until it bleeds!

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