I have plenty of Gardz left over from previous jobs - do you know if it's wise to use it on unsealed marble tiles?
No idea but guessing not as the marble isn't porous like plaster, contact Zinsser Technical Dept for help.
I did message them when I posted here - awaiting response. The marble is unpolished so it is porous, maybe not to the extent of surfaces that Gardz is most commonly used for but Gardz claims to deliver a 'rock-hard' finish.
Look a LTP Mattstone Sealer circa £12 a litre which covers around 10 square metres, excellent sealer though. Look it up and also watch the video.
Can't find it at that price delivered. If all else, fails, Screwfix have No-Nonsense version at £13.99. I have a lot to shell out on adhesive, grout, sealer and diamond blade for half a square metre of hearth.
Zinsser response just in: 'Thank you for confirming the project you are looking to undertake. While Gardz definitely wouldn’t be suitable for this project we may have a product in the Blackfriar range that could lend itself to this application, however this has not been tried and tested for this previously and we would recommend testing on a small inconspicuous area first. Alternatively, you may wish to speak with the manufacturer of the tiles to see if they are able to suggest a suitable solution with a product they have tested on the substrate. Should you wish to try our product this is the Blackfriar Quick Drying Varnish which is available in clear matt, although even this will change the look of the marble just due to the nature of the product. https://www.blackfriar.co.uk/product/quick-drying-varnish/ Applying this will help in being able to wipe or clean the surface however it won’t provide complete protection from stains and there are no guarantees as to how well the product would perform in this unusual application. If you are using this product then 3-4 coats should be applied by brush or roller at a coverage rate of 14m2/L/coat, with a 4 hour re-coat time. I have attached a technical data sheet for the product and I hope this information is helpful to you, however if you require any further assistance regarding this or any other products please do not hesitate to contact me or a member of the Technical Support team.'
Yes as thought really, I would seriously consider the LTP sealer as it will do the job far better than an acrylic varnish and will keep when it comes to freshening the tiles up.
Cheapest I can find on ebay is £14.90 that includes p&p, Wickes may sell it as do ceramic tile retailers. May be best to look online for LTP stockists in your area.