Spray Chrome Troubleshooting Guide

At Angel Gilding we think that the more you understand a process - and the science behind it - the more likely you are to succeed.

We have listed the most common problems with creating a front surface silver mirror and the causes and solutions to those problems. The chart includes links to detailed explanations at the bottom of the page.

To answer one very frequently asked question -- yes, you can certainly use our chemicals in another company's spray on chrome machine. Just rinse the machine thoroughly with distilled water first and be sure to follow our mixing instructions!

Thank you, Gordon Tarpley, for letting us show off your C-3PO and process photos.

TEXTURE OF THE SUBSTRATE

The silver deposited on the surface is 50 to 100 nanometers or 600 times thinner than a human hair. It is much too thin to fill in any surface imperfections on your piece. If you want the silver to look like a mirror, the surface that you silver must first look like glass.

Silver makes any imperfection - any bump or dent in the surface - much more obvious because the light that hits the bump is reflected back on a different path - the 'angle of incidence = the angle of refraction.' Uni-Coat applied to a carefully prepared surface give you the glassy texture you need to create a perfect reflection.

• This ceramic glove has been spray chromed. Clear Uni-Coat is thinner than other clear coats which means it helps to maintain the original texture of your substrate. This could be problematic for uneven pieces or striking for pieces with artistic texture such as this.

SPRAYING ON THE BASE COAT

Uni-Coat flows out to flawlessly smooth, glassy surface when it is applied correctly. Use a 1.0 tip on your gun. The air pressure coming from your HVLP gun should not be greater than 10 psi. Hold the gun 8 to 10 inches away and at right angles to the surface. Apply the Uni-Coat in a sweeping motion. Apply one double wet layer - a thin layer adheres better than a heavy layer. Make sure the entire surface is wet - avoid dry misting which will show up as a matte surface under the silver. Applying a heavy layer can result in runs and drips.

Make sure the Uni-Coat has not begun to dry in the gun. Partially dried Uni-Coat shows up as small nibs on the surface. The temperature of your work space greatly affects the drying time of the Uni-Coat. Clean the gun immediately after use by spraying clean acetone through it.

• This close up shows an even flow of basecoat on the bottom part of the piece with some more uneven texture above.

WETTING THE SURFACE

Water has a high degree of surface tension; water molecules would rather stick to each other than they would to the surface. Most plastics also have a high degree of surface tension so they repel water - they are hydrophobic. When you cover plastic with water, the water beads up and runs off.

A wetting agent - also known as a surfactant - is a substance that breaks the surface tension in water. There are many kinds of surfactants designed specifically for different surfaces. Our Wetting Agent is generic so it works on most surfaces. However, it only works when it is mixed with the water-borne chemical you are trying to apply - in this case the Sensitizer or Tin for Silver. So you must allow the two substances to mix on the surface by applying the Wetting Agent and then adding the Sensitizer.

We have tried pre-mixing the two chemicals, but the chemicals perform better when they are each at their own dilution ratios. Our two-step process is a reliable way to ensure that they both are both able to fully do their work.

• You can see in this close up view, there are areas of white where the silver did not deposit. This is due to insufficient wetting. This is resolved with flaming the basecoat as well as the application of Wetting Agent.

SILVERING BARE PLASTIC

If the plastic you want to silver is already high gloss, you may not need to apply a base coat. You may be able to silver directly onto the very well cleaned bare plastic. We have done this successfully on many plastics.

However, we have found that on some pieces, no matter how well we clean the surface or how much Wetting Agent we apply, the silver still has small gray speckles in it. We have not yet found the exact cause for this. We have found that we can fix the problem by using Uni-Coat base coat.

if you have the same problem, you do not need to discard the piece. Just clean off the bad silver with Silver Remover. Then clean and dry the piece carefully, and apply Uni-coat base coat.

• This image shows that although seemingly high gloss, some plastic should still be basecoated to ensure a smooth application of silver.

WATER FOR SILVERING

Steam distilled or de-ionized water is often available at your local grocery store. Not all bottled water is suitable for mirroring. The bottle you buy must be labeled as "distilled" "de-ionized" or "reverse osmosis". You can pay for a TDS (total dissolved solids) meter if you like, but we have a simple test for water purity and a discussion on how water is purified on our Water Purity page.

• This is a demonstration of our simple water purity test. You can clearly see that this water is not pure enough for the silvering chemistry.

Sensitizer

The sensitizer layer is invisible but it is essential to the silvering process.

The Sensitizer (Tin) layer chemically attaches the silver to the surface. If the surface is not completely covered with Tin, the silver will rub off easily or not deposit. The surface must be clean so the Tin can attach. The water that carries the Tin must be able to contact the surface - see Wetting the Surface.

The Sensitizer must be diluted according to our instructions. If it is too strong, the silver will not deposit evenly or it will be brown and streaky.

The Sensitizer must be carefully rinsed off before silvering. Extra Sensitizer left on the surface will cause brown and yellow stains in the silver. Rinse and then rinse again.

Sensitizer combines easily with oxygen in the water and in the air. When it does, it turns yellow or changes into an insoluble white powder that will not attach to the surface. Keep the bottle capped and store it in a cool location such as a refrigerator.

Adjusting our Pump Spray Assembly

• The bottles must contain about 2 fluid ounces - they do not work well when they are almost empty.
• Both bottles must be fully pressurized. Forcing the piston can break the seals on the pumps.
• Use the adjustment knobs on the tips of the wands to re-balance your gun if necessary. We set the this adjustment before we ship each Pump Spray Assembly.

Adjusting our Center Handle Silvering Gun

• Use distilled or de-ionized water for this test. Do not use silvering chemicals or tap water.
• Measure 500 mL of distilled water into each bottle and attach the bottles to the gun
• Point the gun into a sink or tub, squeeze the trigger and hold for about 30 seconds.
• Remove the bottles from the guns and set them flat on your bench.
• If the bottles have not lost equal amounts of water, adjust the knobs on the end of each gun and try the test again.
• The adjustment knobs can be locked and unlocked with the hex wrench included in the tool packet. 

Silver develops white "clouds"

As we mentioned above, silver adheres to silver. The silver crystals build up exponentially fast. As the 'mountains' of silver crystals grow, the surface becomes rough and less reflective. Instead of a perfect mirror, you begin to see dull, white areas. Adding more silver makes the problem worse. Because the silver is so thin (see above) burnishing does not solve the problem.

To avoid the problem, apply the silver in thin layers and rinse it between each layer.