I first heard about hydrating bait back in the early 1980's from an article all about fishing some difficult Kent lakes. According to the author the carp on some of these lakes would not eat fresh bait. So to give the bait a 'washed out” appearance he began to soak his bait in lake water
Since then 'Hydrating” and 'Glugging” bait has become a standard method in the carp anglers skill set and when I look back at my own fishing this method does stand out as being really effective at times

It works simple as that, but you don't always need to use it and sometimes I believe it can be counter productive. On a busy fishery bait will be going in all the time and the carp soon get used to this. Now depending on their view they might see fresh bait as a safer bet than old (washed out). For instance on one very busy highly stocked lake I fished I noticed that the carp would quite often respond to a few fresh handfuls going in on a new spot but baited spots would produced little. I reasoned that when the bait hit the water the carp (which of course has excellent hearing) would come in and start to freely take the bait but as numbers of free offerings decreased their caution would kick in. In other words they knew that up to a point freshly introduced bait would be safer than old. So in this instance washed out bait wouldn't bring any benefit and could end up working against you

On another lake that very same year I found the opposite to be true. Again a reasonably well stocked lake but with only a few anglers fishing it and plenty of natural food. Here the carp responded well to washed out bait and it increased my catches.
The difference between the two lakes though was clear. In the first lake the carp had to eat bait all the time to survive and the longer bait was laying around the more likely it was to be dangerous for them to pick up plus there was a regular supply of fresh going in. But in the second lake bait would go in infrequently and there was plenty of naturals for them to feed on so fresh bait even though it worked would often lay around before being eaten and they became used to that being safe.

Depending on your method this can give the same washed out look as soaking baits in water however it also boosts the signal of the bait. If you just pour glug over your bait before putting it out or only soak it in glug for a short time the washed out effect will be minimal but you'll get a boosted bait. The more concentrated your glug is the less it will wash out bait too. It all depends on how well you bait absorbs the glug.

There are all sorts of theory's about how to hydrate your bait, one is only using lake water, but to be honest I have never found this to make any difference. Another is to hydrate for a prolonged period, but I feel this is only to allow the bait time enough to absorb the hydrating solution, rather than bring any other benefit. Then there is the issue of how much bait do you hydrate for a session? There is not much point in preparing 5Kg if you're only going to use 3Kg and if you have to wait 24 hours for it to soak then at best you can only take a guess and hope it's enough or not too much?
A much better method would be to have all the benefits of a prolonged soak giving you full absorption and the washed out look plus the ability to only prepare small amounts when needed at a few hours notice
So what is going on when you hydrate bait? Well quiet simply the bait will swell as it absorbs the solution and this in turn opens up the bait and allows more solution to be absorbed. The longer you hydrate the softer and more washed out the bait will become, also the warmer the water the faster this will happen

So I looked at the problem in a practical way and over time I formulated a very simple yet fast and effective method that prepares any amount within a few hours and gives me the exact same result. To be honest it came about when I forgot to hydrate my bait the night before...
First I pour the required amount of glug over the bait I need to prepare, in the case of my Berry glug its around 50ml per kilo of boilies but of course you can use more.
I then pour over hot water to just above the level of boilies, I use water that is just off boiling as this helps prevent any scalding.
The bait will be ready in just a few hours, once it is pour off the solution into the margin or if you want save it for a longer cooler hydrate