Potassium bitartrate or a sediment is not a bad sign
To say it bluntly, crystals in wine are not damaging for your health or a lack of quality, the opposite is true. The gemstones of wine have often already been found in young wines.
What they show is a high volume of minerals in the wine. It is mostly wine crystals or sediment that are found in older, more expensive wines where you will find the crystals on the cork mirror or the bottle partition. This is a sign of long ripening in the bottle.

A wine master will call this old age sediment. It is also recognised by the larger crystals that will be formed in a later stadium. When a very old barrel is lightened up the crystals will shine as if you are in an ice cave.

How do the crystals end up in the wine
The riper the grapes, the larger the share of wine acids. The longer the grapes are on the ranks, the more minerals can be taken from the soil. When those minerals and wine acids meet, more and more wine crystals are being formed. These crystals do not dissolve in the wine, but form itself on the bottle partition, the bottom of the bottle, the cork or already in the barrels.

Wine crystals in the bottle – a sign for odour in the wine
Potassium bitartrate has no influence on the quality of the wine but there still is an interesting relation. A slow fermentation at low temperatures saves and preserves taste and odours in the wine. The slower and longer this fermentation process is lasting, the less of these potassium bitartrates are formed in the barrel and therefore more wine crystals will form in the bottle. This means that cream of tartar in the bottle is a sign of true skill of the cellar master and therefore the quality of the wine.

Potassium bitartrate in the glass, a wrong impression
To emphasise again, potassium bitartrates are not dangerous and do not affect the taste, the colour or the brilliance of the wine; and you can also prevent the wine crystals ending up in the glass.

Red wine livens up with air, it breathes and its structure and volume get better. Why not block the wine crystals at the moment of pouring the wine. Decantation in a carafe is also a good help. To take it to the extreme, hold the bottle in front of a candle, this way you can see if all crystals have been left behind in the bottle.

There is a big difference with white wine. White wine loses its odour and bouquet when aired. Therefore white wine is not decantated because too much air will mix with the wine. White wine is poured out of the bottle very carefully, to leave the wine crystals in the bottle and not letting it get in the glass.