First of all I want to thank Phil from Quality 1 for your interest in this subject, it is by your request that this is here.
Regrouting is a great low overhead money maker, in fact, there is more money in regrouting than reglazing and less exposure to chemicals. The following information is copied from an article I wrote, http://ezinearticles.com/?Regrouting-Tips-And-Advice&id=1032085. If you have any questions regarding the regrouting process after you read this, feel free to post them and I will answer them.=================================================
Regrouting TileRegrouting is the process in which you remove the existing mortar fill between an existing tile installation. Regrouting is a tedious process but can be done successfully with a little patience and perseverance.
The first thing you need to do is establish whether you need to regrout or not by determining whether you have sanded or non-sanded grout. This is important because regrouting should only be done to non-sanded grout joints. There are other methods of restoration for sanded grout joints that are more effective like grout recoloring. Once you determine this it is time to gather the needed tools to complete the job.
There are a slew of tools that can be used to regrout but lets face it, regrouting is a tedious process and the manner in which you remove the grout will determine the time it takes and the quality of the outcome. It is important that you remove at least 1/16 of an inch of grout for the new grout to embed itself in. If you do not, it will surely flake off the next time you clean. I am going to tell you the most important tools to use to make the job easier.
First, for the grout removal process you will need:
* First choice: Roto Zip with a diamond tile cutting blade and attachment (This tool is for an advance user and should only be used by someone who is not afraid of the speed in which it spins. This tool will yield the best results for all field areas but it an also cause damage if not handled properly.
* Second choice: Fein Multimaster with a diamond cutter not carbide. (This tool is for an advance and novice user and is the safest tool for removal but takes a little longer. It has alot of other uses also and in my opinion is a great investment)
* Dremel with tile cutting bit (This tool is for edges, corners and touch-ups)
* Wet or Dry Vac
* Razor Scraper for removing old caulking
These are the most important tools for the removal process and will yield the best results for both minor removal and removal on a large scale. There are other hand tools you can use but are only good for very small jobs.
Next, you will need tools for the grouting process:
* 2 Buckets (One for mixing grout and one for water)
* Grout Float
* Margin Trowel for mixing
* Grout Sponge
* Terry Towels for cleaning, final dusting and sealing
Now you need the supplies to clean and prepare the joints for the new grout and seal the new grout.
* Phosphoric Acid Cleaner
* 511 Impregnating Sealer
* Chemical resistant spray bottle
* Scrub Brush
* 3M Heavy Duty scrub pads
Also, for your protection you will need safety goggles, dust masks, ear plugs and chemical resistant rubber cleaning gloves. This should complete the arsenal for your project. Now we will get to the process.
I am going to assume you chose the Multimaster for your removal tool. Work in areas about 2ft. x 2ft. using long even strokes to remove the grout letting the machine do the work. Remember, you only need to remove about 1/16th of an inch, don't try to go any further you'll just make things more difficult for yourself. Leave about an inch from all corners and edges. Once you finish de-grouting all the field areas next you need to do all the edges and corners and you will do this with the dremel and tile cutting bit. If you want to save some time, just remove the top layer of grout to expose the white underneath cause when you acid wash the tile and grout it will brighten up to a new appearance. When you are done doing corners and edges remove any traces of old caulking with your razor scraper. You are now ready to prepare for the new grout.
Fill your spray bottle about 25% with phosphoric acid and 75% with water and again work in areas about 2ft. x 2ft. starting at the bottom of your project if it is vertical. Spray the acid and scrub with your scrub brush and then clean the tile with the 3M pads and water to remove soap scum. Rinse thoroughly with water and suck up with the wet or dry vac and then dry off further with terry towels. If there are any visual remnants of caulking, try removing it with a little acetone. You are now ready to grout.
There are many colors of grout to choose from but on this project I am going to assume it is standard dry white non-sanded grout. Mix your grout in one of the buckets with your margin trowel to a plyable paste and spread over the tile and grout evenly with your grout float. Then take your grout float and hold at a 45 degree angle to remove the excess mortar and fill the grout joints. When you are finished grouting, go back and wipe smooth with your grout sponge and water rinsing your sponge out frequently. Do not leave too much water in the sponge cause at this point moisture in an enemy. Don't worry about the light haze it will buff off with your towels. When you are finished wiping down let it dry a couple of hours and then buff with your terry towels. Let the project set at least 4-5 hours and seal with the 511 Impregnating Sealer following the manufacturers instructions. When you are all finished, caulk any areas needed such as base of sink, base of tub surround or base of stall shower.
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Also, here is a video I shot. Sorry about the lame video but it was very hard shooting this myself. It took me almost a whole bottle of Zinfandel before I stopped fumbling my words. You can get the general idea though.
