White spots on slate after sealing

[Sergio Antunes]

I had 800sf of Chinese slate installed. The grout was removed with water about 15 minutes after slates were being installed (a large crew did the installation and some were grouting and others cleaming). The next day I washed the entire floor with water a couple of times. After 48 hours I used the penetrating sealer from Aqua Mix. After the first coat dried I noticed some white spots on some slates (see pitcure) and a white hase on others. If I pass my finger over it my figer turns white.

Questions:

1. What is the cause of the white spots?

2. What is the best way to remove?

Thanks in advance.

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[Davestone]

My guess is you got the slate so wet the sealer reacted and didn't dry properly,and may have even got some floating efflourescence involved. I would clean these spots with a scrub pad or brush and water again and put a fan on them, let dry a couple days,and seal them again if they look good. If they reappear,you'll need a 50/50 vinegar wash and water rinse and dry again, then seal,I don't recommend a vinegar wash first cause you might get some discoloration.If this haze stays you might wind up stripping the sealer and starting over,read the back of the bottle and follow their time of drying instructs,and the stripper they recommend.

[KChurch1]

When using penetrating sealers it is very important to wipe off all the excess sealer from the surface of the stone. Penetrating/impregnator sealers are not meant to be topical. It appears from your photo that some of the sealer may have dried on the surface of your stone and dried white. You can try and re-emulsify the sealer by applying a little bit more sealer (same brand) to the white spots and scrubbing with a scrub brush/pad and wipe up the excess. I see this on occassion with the water based sealers.
Or it could be efflorescence... in that case a little vinegar or acidic cleaner should remove it.

[Steven Hauser]

Sergio,
Welcome.
:)

Give what Karen says a try.

It is most likely and easiest to do.

My .02

[Steven Hauser]

Jim I am going to move your inquiry to the Pro forum so that this can be discussed with Todd.

I'll name it Manufacturers rep's the pro's and the con's.

Thank you for your interest.

I'll also make a copy of Todd's so that you can start a reference point.