Ceramic floor tile installation question

Looks like we're installing ceramic floor tile in the living room. I've done plenty of tile work before. Tub surrounds, custom showers, kitchen counters & backsplashes, but never a floor.
Underlayment is 40-yr-old concrete slab. We're pulling up old linoleum floor tile squares from the 60s. These were adhered to the slab with asphalt mastic.
We intend to use thinset to lay the ceramic tiles but don't know if we should attempt to remove the old asphalt mastic first, down to bare concrete. This is NOT an easy or non-messy job. Size of the area would require several gallons high VOC and highly flammable solvent to remove the asphalt. (I should know. I've done this job before, too.)
Can we apply thinset & tile over the old asphalt mastic?
We appreciate knowledgeable answers from experienced individuals.
-Frank
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You would need a polymodified thinset. Your floor would be as strong as the old asphalt mastic.
If you remove to bare concrete, then you would not need the polymodified. I am a profesionall tile layer, I recommend bare concrete.

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wrote:

Thanks, Troy. That puts a name on what I need to do the job one way.
I saw some stuff at HD today; Jasco Sealer & Adhesive Remover http://www.jasco-help.com/products/prod_ft.htm#0221-4 that is advertised to remove old mastic. Sure sounds better than a 5 gallon can of lacquer thinner.
Ever used this stuff or similar?
-Frank
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You will need a good scraper with plenty of blades. Its a lot of work. I have used jasco and it helps soften up the mastic. Gloves are a must so you don't get blisters.

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Every one I know that has tried it with out removing the mastic was LESS than satisfied.
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Try Go-jo the hand cleaner, the plain old white kind works the best.

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Frank Warner wrote:

A 40 year old slab will be very stable.
Not _any_ polymer modified thinset will do. It must state on the bag that it will adhere to "Cut-back" adhesive.
In that circumstance I would use a product called Laticrete 333. (made by Laticrete of course). It is a liquid which you mix with non-polymer modified (plain ol') thinset. It makes the strongest, stickiest thinset I've ever found. If you can't find Laticrete 333, be sure to look carefully on the bags of other thinsets to be sure it sticks to cut-back adhesive.
NEVER trust the sales person...they have no freekin idea what they're talking about. The chemists who create the products, and the companies who guarantee them, are a little smarter than the know-it-all store employee. There are multiple thinsets for many different applications. It is amazing to me that people will trust the dopey guy working the 'tile department' that day, when the bag of thinset itself has very specific printed information on it.
After scraping off all loose adhesive, and washing the floor with clean water, skimcoat the floor with a thin layer of the correct thinset, pressing the skimcoat in with a flat trowel. Pressing or forcing the thinset into the floor helps to create a good bond. Let this dry 24 hours and you'll have a strong thin coat of material over that adhesive that won't want to let go. Then you can use any polymer modified thinset to lay the tiles.
thetiler
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Great information. Thanks a bunch! Printed out so I can refer to it later.
-Frank
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sounds like a diamond grinder w/ some sand ( to help the asphalt based product ball up) would work just fine
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Two thinsets (of many I'm sure) that I know of for this specific application are:
Bostic's D-70 ProFlex Thinset Mortar Roberts' R-Flex III Enhanced Polymer Fortified Thinset Morter
and... a reading link for Frank:
http://www.tileusa.com/cutback-carpetglue_faq.htm
Regards, ed
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