Chapter 1: Pretreatment on Products Before Hydro Dip

Surface cleaning without grease or other impurity is vitally important to a successful hydro dipping process.

Experiences show many hydrographic failures come from poor pretreatment on the products.

Detailed requirements on pretreatment as follows:

1. First, inspect the products if there is obvious impurity on the surface of the products. Polish the surface with 800-1000mesh sandpaper. Carefully don’t polish too hard to leave scrapes on the surface.

2. Touch the products if the surface is smooth. If the surface is rough with sandy feeling, polish it again.

3. Observe the products if there is oil stains, dust or other impurities on the surfaces. Remove the oil stains or dust by proper methods. For example, remove the dust with a clean rag or the stains with a suitable solvent.

4. To remove the inferior pattern from the hydro dipping process, you have to use the special pattern remover.

Or if the area of defects is small, you can use 800-1000mesh sandpaper to remove the defects and trim with paint brushes.

5. The products must keep clean after pretreatment.

6. The products must keep dry after pretreatment. Use an air dryer or blower to remove the moisture on the surface of the products. Or just leave the products in a clean and dry place (air-dry).

7. Place the pretreated products in a clean and dry location for the next process step.

Chapter 2: What kind of paint is used in hydro dipping?

About the base coating, the paint depends on your material that will dip. The paint is the normal paint, not special, but need be compounded with diluent agent and firming agent at a special rate. Certainly, you can ask for some information from the paint shop.

Chapter 3: Which material must be sprayed base coating?

ABS doesn’t need to be sprayed base coating,

PP, PC, PS, PU, PVC, Silicone, Nylon, PA, Metal, Ceramic, all must be base coated. Each paint for base coating must match the subjects to dip. And for some material such as PP, PVC, TPU, PC, PS, you need to spray some primer to enhance the adhesion of substrates. You can consult your local paint seller. About the color of paint, you need to match the color of your substrates.

What is the curing temperature after base coating and top coating?

The temperature for base coating is 65℃ for ABS, PP, PC, PS, PU, PVC, Silicone, Nylon, PA, the baking time is15-20minutes;

the baking time for metal and ceramic is 30minutes;

The temperature for top coating is 65℃ for ABS, PP, PC, PS, PU, PVC, Silicone, Nylon, PA, the baking time is 45 minutes;

The temperature for top coating is 120℃ for metal and ceramic, the baking time for metal and ceramic is 60minutes.

Chapter 4: How to prepare to hydro dip?

1. Before hydro dipping, the products must keep clean and free from static electricity.

2. Ensure the water surface clean. No residue and activator on the water surface. Cleaning the water surface through turning on the water pump for flushing the residue, then remove the bubbles of the water with the dividers slightly and slowly.

Chapter 5: How to distinguish the right side of hydrographics film touching the water?

You have to distinguish the right side of the hydrographics film before dipping. Some hydrographics film the face side is matte, some face side is glossy, if you put the reverse side of the hydrographics film on the water, the hydrographics film won’t work, you can’t dip anything. So you can dip some water with one finger and touch a little corner of the hydrographics film, you can feel one side sticky, so this sticky side is right side towards the water.

Chapter 6: How to lay the hydro dipping film on the water?

Don’t let water drop to the other side when laying hydro dipping film on the water. So you put the film on the water with a dry hand and keep a 30-40degree angle with the water surface. Pull the ends of the hydro dipping film from one end of the hydro dipping tank to the other to avoid air bubbles. If there have some bubbles or film curling, you can remove the bubbles slightly by hand or blow it away by the spray gun. Pay attention not to damage the hydro dipping pattern.

Chapter 7: When to start to spay the activator?

The timing for spaying of activator is also a trick for successful water transfer printing. After the film laying on the water, spraying activator has no fixed time, because many hydrographic films have different activated time depending on the blank hydrographic film, the ink, and the water temperature. The common time of spraying activator is in 45-90seconds. So, you have to observe the change in the film. When the film is spreading flat with light glimmer. Let’s start to spray activator now.

Another way to determine the time of the spray activator, you can spray little activator to the corner of the hydro dipping film, the sprayed corner will turn to a layer like thin oil on the water without wrinkles. Let’s start to spray activator now.

Chapter 8: How much activator spraying to the dip film?

This is something of skill or experience. We just run the spray gun crosswise from left to right or from the top to the bottom lengthwise. Spraying activator only one time, don’t repeat on the activated surface, because this will disturb the hydro dipping patterns. The distance of the gun to water surface is 30-40cm.The liquid flow of spray gun need to be adjusted to maximum, the speed of running spray gun must be slow. The usual amount of activator is 1 liter of activator to activate 30-40sqm hydrographic film by hand.

Chapter 9: How does hydro dipping work

1. Cutting the suitable size dip film, ensure the film can cover the whole article surface. Not too big or too small for saving your film.

2. Pay attention to the dip angle (30-45degrees), ensure that the contact area of the object with water is minimal.

3. Attention the wave direction especially the pattern of wood grain. Or you may decide to turn the film 90°or 180° on the water. The dipping is a continuous one-step procedure, no stop during the dipping process to ensure do the best dipping.

4.when the product dipped into the water, shaking it gently in the water and remove the floating film remains and take it in a tilted angle. Do not allow the product to fall down.

5.when you finish dipping, check if there is any defect on the hydrographic patterns (bubbles or cracks). This may give you an idea for an improvement on next dipping. If it remains to stick to the product, rinse it away with water.

Chapter 10: How long to change the water in the hydro dipping tank?

The water in the tank must be maintained at a certain level.

In hydro dipping process, the water is not only used as media to give pressure for hydrographic dipping it also can wash away the remains. The water needs to change if you find the water is sticky or there are bubbles or lots of remains floating on the surface.

Chapter 11: How to wash after hydro printing?

1. Take care not to touch the product by finger just out of the water. The ink layer at this time is very fragile, any touch may damage the just coated pattern.

2. The purpose of washing is to remove the sticky layer on the surface. Do not apply too heavy a pressure for washing.

The heavy water pressure may damage the just coated pattern.

3. After washing, touch the product by our finger. If you feel sticky on the product, please wash again. The sticky layer must be thoroughly washed away, or the adhesion for the finish coating will be a problem.

4. You may also need to wash the other side (uncoated side) of the product because usually this side also needs to dip for another pattern or apply the finish coat.

Chapter 12: How to deal with the defect product by trimming?

1. Before finish coating, the defected pattern need to be trimmed. The trimmer should prepare the same hydrographic film, activator, suitable tools such as paintbrush and sandpaper for such purpose.

2. Use the paintbrush soaked with the activator to erase the defected area.

3. Trimming is only carried out on defects of the small area. If defects on the large area are found.

This should remove all pattern or cover the whole surface by painting.

4. The trimmer should each product before delivering products to the spray booth.

5. Remove dust or impurity on the trimmed products. Place the trimmed products in a dry and clean place. Which are ready to move to the spray booth for top-coating.

Chapter 13: How to reworked defective products?

1.Instructions on dealing with inferior products before finish coating
1.1 If a pattern s locally damaged you can try to mend it by cutting off a piece of film and dipping again
1.2If a total pattern is damaged, you have to remove the total pattern with sandpaper or solvent and dip again.

2.Instructions dealing with inferior products after finish coating
2.1 If local defects such as dust points or drippings appear on surface finish, polish the local surface with wax
2.2If the whole finish surface is a failure(dripping and primer penetration in a larger area). the finish has to be removed with the solvent for renewal.

Chapter 14: How to dry the dipped products after dipping and top coating?

1. The temperature setting is essential for the baking process. The baking temperature depends largely on the material of the product, The product may be deformed or degraded under elevated temperatures.

2. The temperature setting for drying dipped products after washing.

thermoplastic and nonmetal products: less than60℃;

metal products: Max180℃, because the primer cannot stand higher temperature;

If the products are coated with two component PU paint as a primer, you should observe exactly the paint manufacturer operational instructions. The purpose of drying after washing is no other than removing moisture from the products

3.Curing temperature for top coating:

The baking temperature and time depend on the nature of the finish coating. Finis coat or transparent lacquer or varnish has two types: baking type and non-baking type.

Please follow the manufacturers instructions for curing time and temperature.

Chapter 15: The dip painting method for top coating:

The top coating is a kind of transparent varnish. Paints of a different type may be used for the finish: two-component PU paint, one-component lacquer, baking lacquer gloss, and matte.

Chapter 16: The instructions on finish coat application

1.Preparation: the amount of transparent lacquer prepared depends on the number of products.
2. Prepared lacquer must be filtered with 300mesh nylon screen.
3. Spray booth must be clean, free from dust, The floor and the floor around the spray area must be wet to prevent dust from flying over in the air.
4. Never touch or allow any object to touch the uncured surface.
5. The operator must clean the spray gun before leaving the shifting job

Chapter 17: How to properly use and maintain the spray gun

1. Clean the gun with activator before the operation

2. The key for a successful dipping process: a. the right time (when the film is totally soaked and softened) for spraying;

3. The amount of activator applied to the film. So you have to adjust the adequate spraying amount, not too less or too much.

4. You need also adjust the air pressure, activator flow and the width of fine spray.

5. Lower air pressure results in less activator spray and vise verse.

6. Move the gun at an adequate speed not too fast or too slow.

7. The amount of activator is related to the expansion of the film (ink layer on water). In general the bigger expansion, the higher amount and vise verse.

8.On larger spray area (or larger film size). there must be 1/2 overlap between each passage of gun move. This can prevent the porous defects caused by activator volatility.

9. The newcomer may use water as the activator for training purpose. After training. the gun has to be cleaned with the activator or it will get rusty.

Chapter 18: How to do Quality Control and Packing after finishing paint dipping process

1. The checker should timely find the problem and report to process technician to reduce the loss to the maximum.

2. First, check if the product is clean and dry.
3. Then check the pattern if there are holes(porous points)and cracks on the pattern.
4. Check if the trimmed surface is clean and the wave color is the same as the sample.
5. Check if there is dust, dripping and peeling on the paint.
6. The passed product can deliver to packing.

Chapter 19: The reason and solutions for defects in the transfer printing process

Pitting, porous holes, small bubbles or rough surface on transferred pattern surfaces.

Reasons:

a. Poor spray booth environment dusts in the air. Dust on products and film surface
b. The water surface is not clean: floating impurities and remains.
c. The film did not lay evenly on water. Bubbles exist between film and water surface. Water temperature is too high. The compressed air is not clean, the air is mixed with moisture oil and other Impurities (the film ink would not be fully activated and there are water drops and oil drops on the film).
d. Not enough activator sprayed or unevenly sprayed
e. The activator evaporated too fast: activating time is not enough. the film ink has not been activated to oily state(ink peel on the pattern: During the transfer printing process, the wat should be expelled from between the product and ink. The not fully activated ink may hinder expelling of water).
f. The dipping angle(normal 45°) is not correct or dipping too fast. That caused bubbles and water drops enrolled in between the product and the pattern ink.

Solutions:

1. The spray room must be clean. Spray wat on the ground to prevent dust from being over. Clean dust from product surfaces and work table. Do not allow dust on ink surfaces
2.Wipe with a scape the remains away from wat surface
3. Pull the hydro dipping film gently from one end of the tank to the other at an angle of 45° (to remove any impurities and bubbles on water)
4. Check water temperature. Experiences tell 25℃-30℃ is the right temperature, Install a water separator to the air compressor. Disconnect the spray gun tube and clean away moisture and oil drops inside the tube to ensure cleanness of the compressed air.

5. Adjust air pressure, atomization value to increase activator flow. Ensure there is 1/2 overlap between the spray passages (never spray repeatedly on the film).On a fully activated ink layer.you may find oily light glimmering

6. Change the activator from the fast-dry type into slow-dry. Adjust the spray gun to increase activator flow. Reduce the gun moving speed. Wait until the pattern ink fully activated to oily state.

7. Adjust the dipping angle to 45ºLower the product down gently and slowly to  hydrographics tank so as to remove air bubbles from between the product and ink layer.

2.Obvious winkles and overlaps at corner position after dipping Reasons.

a. Water temperature is too low. (This causes the film not fully soaked or softened)
b.Soaking time(the time of film laying on water)is not enough(this causes the film not fully softened
c. Too early to spray activator to the film(This causes the tension of the ink layer and that of the ground film is not equal. The ink layer is shrunk with wrinkles on surfaces)
e.The patterned ink has not been activated to oily state(This causes the ink peel to appear on pattern surfaces)

Solutions:

a.Raise the wat temperature to about 25℃-30℃
b.Leave the film on water longer(the soaking time is about 120″ at 25℃water temperature).To see if the film is fully soaked or not, you may make a small test as follows: spray activator on a corner of the film. If the sprayed area appears no wrinkle and it is slightly stretched, then the soaking time is ok.

c.Do not spray until the film is completely softened and the surface tension is OK uniform.

d.Do not dip until the film ink is completely activated.

3. The pattern layer peeled off and the ground layer appears: the pattern wave is a blur; the waves appear broken; the pattern appears different in wave color shade 

Reasons

a. Activator sprayed too much (Over applied activator will cause slipping between the ink layer and the ground film. The of the pattern will be distorted because of such slipping).
b. The primer is too hard or over-cured(The over-cured prime is resistant to activating effect and reduces the surface between the ink layer and the ground material and will lead to the pattern deformation from slippage and shrinkage).

c.Soaking time too long(The ground film will be dissolved because of too long soaking time. Then the ground film losses function to support the ink pattern. The resultant pattern will be distorted or appear broken and over-stretched.

d.The air flow of the spray gun is too strong(The air flow blows the pattern disorder).
e.Activated time too long. (An over-activated ink pattern is floating and moving on water and the resultant picture on the product is blur, unclear).
f.The solubility of the activator is not enough. The film ink has not been fully activated. (This may lead to discontinuous pattern waves and over-stretched pictures).

g.Dipping is not correct(This may lead to pattern shade and color difference).

Solutions:

a. Adjust air pressure and atomization value to reduce activator flow.
b. Choose the right primer. Adjust the hardness and curing of the primer.

c. Reduce the soaking time (120seconds at 25℃ water temperature) to ensure the film is not over-dissolved.
d. Adjust air pressure of the spray gun. The air flow should not be so strong as to blow mess of the pattern.
e. In general, dipping should start in 60 seconds after activator spraying.
f. Change the activator with higher solubility. Anyway, the solubility of an activator should not be adjusted too high)
g. Dip correctly. The correct start position is always where activator spray starts first and dipping at 45°(This is to ensure uniform waves and color shades of the pattern).

If you are interested in hydro dipping or you have some other question after you read this article , please don’t hesitate to contact us.