# Secret Key e-liquids, the Secret's Keys range key by key > The Secret Key range from Secret's Lab key by key, the exact maths of a nicotine shot in the 60ml bottle and the nicotine salt versions. Type secret key into a search engine and you will mostly find password managers, cloud credentials and Korean skincare. In vaping, the name points to a French e-liquid range sold mainly as a shortfill. That is where the questions start, because the bottle is not quite the size people expect and the strength you end up with is never a round number. Here is how to read the **Secret Key** range and work out its strength properly. ## Secret Key, what the Secret's Lab range actually is The **Secret Key** that vapers look for is really called Secret's Keys. It is an e-liquid range from the French manufacturer Secret's Lab, where each recipe is named after a coloured key, from the Blue Key to the Golden Key, alongside a few recipes with their own names such as Secret's Love. The range comes in three forms. The main one is a 50ml nicotine-free shortfill, supplied in a 60ml bottle and balanced at 50/50 between propylene glycol (PG) and vegetable glycerine (VG). Several keys also come as 10ml nicotine salt e-liquids, and some as 30ml concentrates for home mixing. Those three formats are not bought for the same purpose. The shortfill is prepared before use, the 10ml salt goes straight into a pod, and the concentrate is never vaped neat. ## The keys one by one, red fruit, lemonade and desserts The colour names say nothing about the flavour. The descriptions below follow the product pages of two French retailers, which agree on the essentials, and they fall into three families. ### The fruit keys The Blue Key pairs two raspberries, a wild raspberry and a blue raspberry, on a tangy profile that one of the pages describes as neither cooling nor menthol. The Purple Key is a red fruit blend (strawberry, raspberry, blackberry and blueberry depending on the retailer). The Rainbow Key brings together apricot, pineapple and mango. Secret's Love matches dragon fruit, also called pitaya, with strawberry, with a cooling note mentioned by both sources. The Yellow Key also mixes pitaya and raspberry, with lemon and cactus. ### The sharp key The Pink Key is presented as a lemonade flavour lifted with strawberry and raspberry, and one retailer adds a cooling touch to it. Lemon leads the recipe, which makes it a better match for people who like bright profiles than for fans of rounder blends. ### The dessert keys The Golden Key leans towards custard, with vanilla and salted butter caramel. The Black Key is bolder, combining popcorn, butter cookie and caramel. Both recipes carry more sweet flavourings, and sweeter liquids generally tend to gunk up a coil faster than a light fruit blend. | Key | Listed profile | Family | |---|---|---| | Blue Key | Wild raspberry, blue raspberry | Fruit | | Purple Key | Red fruits | Fruit | | Rainbow Key | Apricot, pineapple, mango | Fruit | | Secret's Love | Pitaya, strawberry, cooling | Fruit | | Pink Key | Lemon lemonade, strawberry, raspberry | Sharp | | Golden Key | Vanilla, salted butter caramel, custard | Dessert | | Black Key | Popcorn, cookie, caramel | Dessert | ## Adding a nicotine shot to a Secret Key shortfill, the exact maths The large format is sold without nicotine for a regulatory reason. In the UK, as across Europe, nicotine e-liquid may only be sold in refill bottles of up to 10ml, at no more than 20mg/ml. The 50ml bottle is therefore 0mg, and nicotine is added separately as a 10ml nicotine shot, often at 18 or 20mg/ml. ### One shot, 60ml at 3.33mg/ml The sum fits on one line. Multiply the shot volume by its strength, then divide by the total volume. A 10ml shot at 20mg/ml poured into a 50ml **Secret Key** shortfill gives 200mg of nicotine spread across 60ml, which is 3.33mg/ml, and it fills the bottle exactly. With an 18mg/ml shot the result is 180mg in 60ml, so 3mg/ml. That difference matters when you compare it with a ready-made 10ml bottle, as our guide on [how to lower nicotine strength](/uk/lower-nicotine-strength/) explains. ### Two shots, 70ml that will not fit in the bottle Two 20mg/ml shots take the mix to 400mg in 70ml, which is 5.71mg/ml. This is the detail product pages mention least clearly. The original bottle holds 60ml, so there is 10ml of space missing for the second shot. The fix is to pour the liquid into an empty graduated bottle of at least 70ml, then add both shots. One of the pages consulted suggests a 100ml bottle for higher strengths. The mix then needs a long shake so the nicotine spreads through the whole volume. The final ratio also depends on the shot itself, which states its own PG/VG split on the label. A 50/50 shot keeps the recipe balance, while a higher PG shot shifts it slightly. ## Shortfill or nicotine salt, choosing by device The right format depends less on flavour than on the device that will take the liquid. The two versions are aimed at different kit. The 50/50 of the shortfill suits most tanks and pods running standard coils. The nicotine salt versions, sold in 10ml at 10 or 20mg/ml, exist at least for the Blue Key, the Purple Key, the Golden Key and Secret's Love. They are mainly meant for low-wattage pods, the use nicotine salts are sold for. A vaper who gets through little liquid does not always benefit from the large format. An opened 60ml bottle takes a long time to finish, and how long a bottle really lasts depends mostly on the device, as our article on [how long 10ml e liquid lasts](/uk/how-long-does-10ml-e-liquid-last/) shows. ## Finding a Secret Key without picking the wrong format The range name circulates under several spellings, and product listings often mix formats on a single page. Three checks avoid the most common mistake, which is receiving a concentrate instead of an e-liquid. 1. The volume. A 50ml is vaped after adding a shot, a 30ml is a flavour concentrate to be diluted in a base, a 10ml is ready to use. 2. The word "Salt" in the name, which marks the nicotine salt version. 3. The key itself, since two similar colours have nothing in common on the palate. The 30ml concentrate is meant for home mixers. It is blended into a neutral base at the strength printed on the bottle, and it should never be poured neat into a tank. ## FAQ A few questions come up again and again when ordering or preparing a bottle from the range. Here are the short answers. ### Can a Secret Key shortfill be vaped without a nicotine shot? Yes. The liquid is nicotine-free as sold and can be vaped as it is. The shot is only an option, and the spare room in the bottle simply stays empty. ### Are all the keys cooling? No. Secret's Love lists a cooling note, which one retailer also gives to the Pink Key, while the Blue Key is described without any cooling effect. The dessert keys, Golden and Black, are not presented as cooling. ### Can two keys be mixed in one bottle? Technically yes, since the shortfills share the same 50/50 ratio. You need a large enough empty bottle, and the result on the palate is unpredictable. Try a small amount before mixing two full bottles. ### Does the liquid need to rest after adding the shot? The liquid is already finished, so no steeping time is needed as it would be for a home mix. It does need a shake of several dozen seconds, because the nicotine will not spread through 60 or 70ml on its own. ### Does a nicotine salt shot work in a shortfill? Yes, the strength calculation stays the same, since it depends only on the volume and strength of the shot. The throat feel may differ from freebase nicotine, though, depending on the liquid and the device. ## Secret Key, choose the key before the format The Secret's Keys range is read in two steps. First the flavour family, fruit, sharp or dessert, which tells you whether the recipe suits you. Then the format, which depends on your device and the strength you are after. Above all, remember the maths. One 20mg/ml shot in the bottle gives 3.33mg/ml, two shots give 5.71mg/ml but need a bigger bottle. A **Secret Key** prepared this way is vaped at the strength you intended, and the same holds for any shortfill, whose strength is worked out before it is poured. ## Related reading - [How to lower nicotine strength on a vape, step by step](/uk/lower-nicotine-strength/) - [How long does 10ml e liquid last in the UK](/uk/how-long-does-10ml-e-liquid-last/) - [Nicotine free vape, what actually changes](/uk/nicotine-free-vape/) Editorial content for adult readers only. Vaping products can contain nicotine, a substance that causes addiction. Nicotine vaping products are not for sale to anyone under 18 in the UK. This article is not a buying recommendation and is not personalised advice.