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How To Avoid Dye Migration: A Simple Wet-White-Cloth Fabric Test
Ignored more than any other tip, this is still the single most critical thing a new doll owner can be told. Permanent from the moment it happens, dye migration is the transfer of colour from dark fabric onto the doll's skin. Attempt every cleaning product and approach going and scrub all day; a stain that's been absorbed into TPE won't come out. It costs nothing and takes two minutes: the uncomplicated test that prevention starts with, and prevention is the only defence.
 
Every Skin Tone Is at Risk
There's a chemical reason behind all this. Like water soaking into a sponge, dye migrates from the fabric into the TPE, because TPE is an oil-based material and dark dyes are normally oil-soluble. It begins the moment fabric touches skin and speeds up with heat and pressure, so a dark dress left on a doll for a few hours in a warm room can cause a permanent stain. You can't miss dark marks on a pale doll, which makes it particularly visible there, but every skin tone gets it to some degree.
 
The Test Itself Is Straightforward
There's nothing involved about the test itself. Snip a small piece of the fabric from somewhere it won't be seen; an inside seam is ideal. Wet it thoroughly with clean water. Then take a white cloth, a cotton bud, or a piece of kitchen paper, and rub the wet fabric firmly against the white cloth for about thirty seconds. When any colour transfers to the white cloth, it's a fail: the fabric will stain your doll, and she shouldn't wear it. No colour on the white cloth? The fabric is safe, so use it without worry.
 
Moisture Is the Trigger
Simulating the moisture naturally present on the doll's skin, water activates the dye transfer in the test just as that moisture does in real life. You want a worst-case scenario, and testing with water gives you one, because wet fabric on damp skin transfers more dye than dry fabric on dry skin. A fabric that passes the water test is safe for normal use. There's no way around it: a fabric that fails will stain.
 
Two Minutes vs Permanent Marks on Her Thighs
Run the test again for each new piece of clothing, same brand or not. Dye batches vary and manufacturing processes change, so last year's safe fabric might not be safe this year. In two minutes the test settles whether you have a doll that looks great for years or a doll with permanent dark marks on her thighs. There's no excuse for skipping it, and the purchasers who learn this the hard way are the ones who end up acquiring replacement dolls.
 
Black, Dark Red, Dark Blue and Dark Purple
Failing the test most often: dark colours, cheap dyes, and anything that feels slightly waxy or coated. Black, dark red, dark blue and dark purple offend worst, since the dyes are concentrated and oil-soluble. Bright neon colours are also hazardous, because they use substantial quantities of pigment. Fabric that's been dyed cheaply is more likely to bleed than fabric that's been dyed properly, which is why costly clothing is regularly safer than cheap clothing, even though the difference isn't guaranteed.
 
Safer Choices for Doll Clothing
Safest of all are light colours, natural fibres, and anything pre-washed. Almost consistently safe are white, cream, beige and pale pastels, since there's not enough pigment to cause visible staining. Cotton, linen, and other natural fibres tend to hold dye more firmly than synthetics, which means they're less likely to bleed. Less excess dye is left in pre-washed fabric, because most of it has already been released; transfer onto the doll is thus less likely. Any new clothing should be pre-washed before it goes on the doll, when in doubt.
 
Before You Give Up on a Fabric
Before you bin a fabric that fails the test, there are a few things you can attempt. Attempt a number of hot washes with a small quantity of white vinegar; the idea is to help set the dye and minimise bleeding. Salt binds the dye to the fibres, acting as a mordant, so leaving the fabric in a saltwater solution overnight can also help. Some fabrics are hopeless and will bleed no matter what you do, and these approaches don't consistently work, but wanting a precise piece of clothing badly enough makes them worth trying.
 
Minimising the Risk
If a fabric still fails after washing, the safest alternative is to not use it. Replacing a piece of clothing costs far less than a new doll, and a stain on a doll is permanent.You might be attached to the fabric and want to use it in any case; if so, a few mitigation strategies are there. Line the inside of the clothing with a light-coloured fabric, which creates a barrier between the dark dye and the doll's skin. The other way is to use the clothing for short periods only and take it off right away after use. Not foolproof, either of them, but they reduce the risk.
 
Where to Shop Safely
Clothing for a doll is safest acquired from a seller who understands dye migration and has tested their fabrics. Their awareness of the issue, which is normal among doll-specific clothing brands, shows in their choice of fabrics, so their clothing is more costly but also more reliable. Generic clothing from high street shops is a gamble, and the cheaper the clothing, the higher the risk. Purchasing generic? Consistently test it before use.
 
Wash Several Times Before Use
You should know about a seasonal factor too. Dye migration is worse in warm weather, because heat accelerates the process. Summer might bring a failure for a fabric that passed the test in winter, particularly if the doll is stored in a warm room. Summer purchases of new clothing deserve a more detailed test and, possibly, a number of washes before use. The same goes for a doll stored in a warm room, where the heat will cause any residual dye to migrate faster.
 
The Dye Spreads Through the Material
It pays to comprehend the stain itself, if it occurs. Spreading through the material instead of sitting on the surface, the dye makes dye migration stains normally diffuse rather than sharp. No crisp fabric outline appears; the area just darkens or discolours normally. As the stain spreads and deepens, it goes from hard to spot at first to more apparent over time. When it's set, it's set: it can't be removed, so the only choices are to cover it with clothing or accept it as part of the doll's history.
 
Staying away from False Results
How you test matters as much as the test itself. Don't skimp on the thirty seconds of rubbing, because a fast rub can miss a slow bleed. Scrub like you mean it, as though a stain needs removing, because that's the pressure the doll's skin will put on the fabric. A soiled patch from a previous test would muddy things and give a false result, so each test needs a fresh section of the white cloth. Don't test it dry; test the fabric wet, since water is what activates the dye transfer.
 
The Dark Parts Are the Ones That Bleed
In a fabric with multiple colours, the darkest section is the one to test first. Pass on light, fail on dark: a fabric might do both, and the dark sections are what will stain the doll. Be especially attentive of dark patterns on a light background, where the dark parts are the ones that bleed, and test each colour separately when you're not sure.
 
Why You Can't Time It Safely
So how long does the fabric have to be in contact with the doll for staining to happen? The answer is that it varies hugely, and it depends on the fabric, the temperature, and the pressure. Within an hour some fabrics will stain, whereas others take days or weeks. Assume it'll stain finally. A fabric that fails the test should be prevented entirely. Don't look for a safe exposure time with a fabric that bleeds; the bleed is cumulative and irreversible.
 
Inspecting a Second-Hand Doll
Dye migration is worth checking before purchase for anyone acquiring a used doll. Look at the most typical regions for staining, the thighs, back and buttocks, for dark patches. Apparent dye stains are permanent and affect the doll's appearance, so a soiled doll is worth less than one without them. A stained used doll shouldn't fetch full price; factor in the cost of covering the stains, whether with clothing or a new body.
 
Test Every New Piece of Clothing
Of all the maintenance habits a doll owner can develop, the wet-white-cloth test is the single most vital. What you get for two minutes and no outlay is protection against the most widespread cause of permanent damage. Get into the habit of testing every new piece of clothing, even when you're in a hurry. Five minutes saved by skipping the test is a bad trade if it costs you a doll. More info at this rosslink. Also check out  dig this (https://mybb.nord.net/showthread.php?tid=635) for more.