Archive for January, 2015

TO:  Multi-Tech Products

I am trying to repair a hairline crack in a vitreous china (white Kohler K6652) service sink.  Which product would you recommend and what color white?

Unfortunately, a hairline fracture in vitreous china means there is a crack all the way through the fixture.  Vitreous china can be repaired and even glued back together with our colored Poly Paste product, and we have it in Kohler white.   However, the issue is how to get the Paste into the fracture.  Unless there are separated (broken)  pieces  than can be glued together, you would have to grind a “V” groove through the entire thickness of the sink.   Creating this “V’ groove would produce more damage to the surface than the original hair-line fracture, since it would be very visible.   Also, the back of the unit would need some kind of reinforcement to hold it together.  This procedure could be used if there is good access to the sink, but there are complications.

The repair would be complicated and require a refinish of the whole sink. The next question would be,  “should a service sink be completely refinished?”   The answer is no.  A service sink probably gets too much use and is exposed to damaging impacts, so a refinish would not last very long.  It could also be exposed to strong cleaning chemicals, which would cause the refinished surface coating to fail.

If it is sufficient to achieve a fix simply to prevent leakage through the crack, it could be repaired as described above. Be aware of the aesthetics limitations, and I would not give any kind of warranty.

Many things to think about. But, it is just wise to sometimes walk away from certain jobs. And sometimes, a technician needs to just make things functional too.

Hope this helps,



TO: Multi-Tech Products

I am a spa dealer with a customer that has reported a problem on the surface of his acrylic spa. The attached photos show marks appearing on acrylic shell surface. They were in the area around the filter canister, and looked small stone chips that you get on the front end of an automobile. The customer is one off our best on chemical management and takes great care throughout the year to service his tub.

Can you take a look at the pictures and give me your thoughts on the potential cause?  I have never seen this type of issue on a shell. It’s within about a 12″ area within the filter housing but doesn’t seem to be anywhere else.  Could it involve a previous surface repair?




To: Tony

The pictures indicate that this is another example of acrylic pigment fading and/or topical blistering due to exposure to a strong sanitizing agent (oxidizer).  Although rare, we have seen several similar examples over the years.  One acrylic manufacturer has even been able to duplicate this phenomena in the lab using “Tri-Chlor” tablets.  Someone has created this problem with pool chemicals either by using the wrong chemical, or using too much of an approved chemical. The appearance is consistent with what we have experienced with Tri-Chlor.


The logical mechanism of your example is that a very strong oxidizing chemical (probably in solid form) sunk into the water, fell down the vertical surface creating surface damage as it sunk into the bottom of the foot well or seat.
Acrylic is by far the best material for spa construction, and withstands many harsh conditions, but it is not perfect.
Although this type of damage is rare, it suggests that the industry should increase it’s communications on chemicals to avoid, and how to use the recommended ones.  There is evidence of extreme chemical dispersion into the filter housing, and it reached a very high localized concentration.

From my observations from the photos, I see:

1. A peeling effect of acrylic. This could happen where a tablet would set for a period of time in one spot on the acrylic.

2. A scratching effect. This can be where a large round tablet would float and roll around creating damage to the surface. Or the scraping of chemical damaged or repaired acrylic.

3. Rust in the affected areas. This would be from iron in the water reacting with the oxidizer, and depositing on the porous surface created from the chemical damage.

4. Attack on the silicone in this area also suggests the presence of strong chemicals in the same area.

5. Bleaching of the black filter fixture is an additional indication of chemical oxidation.

If there is a repair in this area, the peeling would be of a clear coat. However, the same chemical damage, described above, most likely would have caused the damage to the repair.  A pre-existing repair could only be determined by inspection by a repair pro that has experience with chemical damage.

The good news is that it can be removed by sanding through the oxidized layer (chemical damage) down to good acrylic.  Then it can be buffed and polished to a higher gloss. It will depend on how thick the oxidized layer is, which depends on how long the acrylic surface was exposed to the high concentration of oxidizing chemicals.  Hopefully, the discoloration is only “skin” deep. From my experience, it looks like it is less than a 1/16″ (1.6mm) deep.

The colors could change as you sand, and become darker or lighter.  It would be unpredictable based on the pigment mixing through the sheet. That should not be a big problem since it is in the filter area where it is hidden from view.   The gloss would be maintained through the proper buffing and polishing process.  If there is a repair, you should find a light-colored filler under the repair coating.  In this case, depending on the repair filler depth, it would need repair including a new coating and clear coat for protection. It could have been a surface repair that just covered up a light surface issue, and may buff and polish out to a normal appearance as well.

Here are other examples of the chemical issues and more explanations of causes. Follow the links in the articles to the proper remedies:

To repair the surface, sand with a progression of 220, 320, 400 grit sandpaper. Finish with 600 grit wet/dry sandpaper. Then to recover the gloss, buff using a high-speed (variable to 2500rpms) with a good quality buffing pad and medium grit buffing compound.
We have a video demonstrating the entire procedure, and it can be down loaded.


Rob Clos